diff --git a/Make.config b/Make.config
index 7b295582e683..221c97d628e3 100644
--- a/Make.config
+++ b/Make.config
@@ -289,9 +289,11 @@ XAMARIN_IPHONEOS_SDK     = $(MONOTOUCH_DEVICE_SDK)
 XAMARIN_WATCHSIMULATOR_SDK = $(MONOTOUCH_PREFIX)/SDKs/Xamarin.WatchSimulator.sdk
 XAMARIN_WATCHOS_SDK        = $(MONOTOUCH_PREFIX)/SDKs/Xamarin.WatchOS.sdk
 
-SIMULATORWATCH_SDK         = $(XCODE_DEVELOPER_ROOT)/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator$(WATCH_SDK_VERSION).sdk
-SIMULATORWATCH_CFLAGS      = -arch i386 -mwatchos-simulator-version-min=$(MIN_WATCHOS_SDK_VERSION) -isysroot $(SIMULATORWATCH_SDK) $(CFLAGS) -g $(IOS_COMMON_DEFINES)
-SIMULATORWATCH_OBJC_CFLAGS = $(SIMULATORWATCH_CFLAGS) $(COMMON_SIMULATOR_OBJC_CFLAGS) 
+SIMULATORWATCH_SDK           = $(XCODE_DEVELOPER_ROOT)/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator$(WATCH_SDK_VERSION).sdk
+SIMULATORWATCH_CFLAGS        = -arch i386 -mwatchos-simulator-version-min=$(MIN_WATCHOS_SDK_VERSION) -isysroot $(SIMULATORWATCH_SDK) $(CFLAGS) -g $(IOS_COMMON_DEFINES)
+SIMULATORWATCH64_CFLAGS      = -arch x86_64 -mwatchos-simulator-version-min=$(MIN_WATCHOS_SDK_VERSION) -isysroot $(SIMULATORWATCH_SDK) $(CFLAGS) -g $(IOS_COMMON_DEFINES)
+SIMULATORWATCH_OBJC_CFLAGS   = $(SIMULATORWATCH_CFLAGS) $(COMMON_SIMULATOR_OBJC_CFLAGS) 
+SIMULATORWATCH64_OBJC_CFLAGS = $(SIMULATORWATCH64_CFLAGS) $(COMMON_SIMULATOR_OBJC_CFLAGS) 
 
 DEVICEWATCH_SDK         = $(XCODE_DEVELOPER_ROOT)/Platforms/WatchOS.platform/Developer/SDKs/WatchOS$(WATCH_SDK_VERSION).sdk
 DEVICEWATCH_CFLAGS      = -arch armv7k -mwatchos-version-min=$(MIN_WATCHOS_SDK_VERSION) -isysroot $(DEVICEWATCH_SDK) $(CFLAGS) -fembed-bitcode $(IOS_COMMON_DEFINES)
@@ -486,8 +488,9 @@ ifdef INCLUDE_DEVICE
 DOTNET_WATCHOS_RUNTIME_IDENTIFIERS=watchos-arm watchos-x86
 DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_32=watchos-arm watchos-x86
 else
-DOTNET_WATCHOS_RUNTIME_IDENTIFIERS=watchos-x86
+DOTNET_WATCHOS_RUNTIME_IDENTIFIERS=watchos-x86 watchos-x64
 DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_32=watchos-x86
+DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_64=watchos-x64
 endif
 endif
 
diff --git a/dotnet/package/Microsoft.watchOS.Runtime.watchos-x64/package.csproj b/dotnet/package/Microsoft.watchOS.Runtime.watchos-x64/package.csproj
new file mode 100644
index 000000000000..87ceff7013b8
--- /dev/null
+++ b/dotnet/package/Microsoft.watchOS.Runtime.watchos-x64/package.csproj
@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <_PlatformName>watchOS</_PlatformName>
+    <_RuntimeIdentifier>watchos-x64</_RuntimeIdentifier>
+  </PropertyGroup>
+
+  <Import Project="../microsoft.runtime.csproj" />
+</Project>
diff --git a/dotnet/targets/Xamarin.Shared.Sdk.DefaultItems.targets b/dotnet/targets/Xamarin.Shared.Sdk.DefaultItems.targets
index e1c1ded4480b..e9e865bba8bf 100644
--- a/dotnet/targets/Xamarin.Shared.Sdk.DefaultItems.targets
+++ b/dotnet/targets/Xamarin.Shared.Sdk.DefaultItems.targets
@@ -59,7 +59,7 @@
     <!-- Runtime pack identifiers -->
     <_RuntimePackRuntimeIdentifiers Condition=" '$(_PlatformName)' == 'iOS' ">ios-x64;ios-arm64;ios-arm;ios-x86</_RuntimePackRuntimeIdentifiers>
     <_RuntimePackRuntimeIdentifiers Condition=" '$(_PlatformName)' == 'tvOS' ">tvos-x64;tvos-arm64</_RuntimePackRuntimeIdentifiers>
-    <_RuntimePackRuntimeIdentifiers Condition=" '$(_PlatformName)' == 'watchOS' ">watchos-x86;watchos-arm</_RuntimePackRuntimeIdentifiers>
+    <_RuntimePackRuntimeIdentifiers Condition=" '$(_PlatformName)' == 'watchOS' ">watchos-x86;watchos-x64;watchos-arm</_RuntimePackRuntimeIdentifiers>
     <_RuntimePackRuntimeIdentifiers Condition=" '$(_PlatformName)' == 'macOS' ">osx-x64</_RuntimePackRuntimeIdentifiers>
   </PropertyGroup>
 
diff --git a/mk/mono.mk b/mk/mono.mk
index 29c76091c4f6..dc9da703aee6 100644
--- a/mk/mono.mk
+++ b/mk/mono.mk
@@ -1,4 +1,4 @@
-NEEDED_MONO_VERSION := be2226b5a1c57df065efc4c1cf008d581e5cec7d
+NEEDED_MONO_VERSION := ac596375c762c6b8dbe3c802f0ce626004eab51c
 NEEDED_MONO_BRANCH := 2020-02
 
 MONO_DIRECTORY := mono
diff --git a/mk/rules.mk b/mk/rules.mk
index e2c7b59105ab..bfcf325bbc33 100644
--- a/mk/rules.mk
+++ b/mk/rules.mk
@@ -8,6 +8,7 @@ DEV7s_I := $(COMMON_I)
 DEV64_I := $(COMMON_I)
 
 SIMW_I  := $(COMMON_I)
+SIMW64_I  := $(COMMON_I)
 DEVW_I  := $(COMMON_I)
 DEVW64_32_I := $(COMMON_I)
 
@@ -91,19 +92,34 @@ define NativeCompilationTemplate
 ## watch simulator
 
 .libs/watchsimulator/%$(1).x86.o: %.m $(EXTRA_DEPENDENCIES) | .libs/watchsimulator
-	$$(call Q_2,OBJC,  [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_OBJC_CFLAGS) $$(EXTRA_DEFINES) $(SIMW_I) -g $(2) -c $$< -o $$@
+	$$(call Q_2,OBJC,  [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_OBJC_CFLAGS)   $$(EXTRA_DEFINES) $(SIMW_I) -g $(2) -c $$< -o $$@
 
 .libs/watchsimulator/%$(1).x86.o: %.c $(EXTRA_DEPENDENCIES) | .libs/watchsimulator
-	$$(call Q_2,CC,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_CFLAGS)      $$(EXTRA_DEFINES) $(SIMW_I) -g $(2) -c $$< -o $$@
+	$$(call Q_2,CC,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_CFLAGS)        $$(EXTRA_DEFINES) $(SIMW_I) -g $(2) -c $$< -o $$@
 
 .libs/watchsimulator/%$(1).x86.o: %.s $(EXTRA_DEPENDENCIES) | .libs/watchsimulator
-	$$(call Q_2,ASM,   [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_CFLAGS)      $$(EXTRA_DEFINES) $(SIMW_I) -g $(2) -c $$< -o $$@
+	$$(call Q_2,ASM,   [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_CFLAGS)        $$(EXTRA_DEFINES) $(SIMW_I) -g $(2) -c $$< -o $$@
 
 .libs/watchsimulator/%$(1).x86.dylib: | .libs/watchsimulator
-	$$(call Q_2,LD,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_CFLAGS)      $$(EXTRA_FLAGS) -dynamiclib -o $$@ $$^ -L$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/lib -fapplication-extension
+	$$(call Q_2,LD,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_CFLAGS)        $$(EXTRA_FLAGS) -dynamiclib -o $$@ $$^ -L$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/lib -fapplication-extension
 
 .libs/watchsimulator/%$(1).x86.framework: | .libs/watchsimulator
-	$$(call Q_2,LD,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_CFLAGS)      $$(EXTRA_FLAGS) -dynamiclib -o $$@ $$^ -F$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/Frameworks -fapplication-extension
+	$$(call Q_2,LD,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH_CFLAGS)        $$(EXTRA_FLAGS) -dynamiclib -o $$@ $$^ -F$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/Frameworks -fapplication-extension
+
+.libs/watchsimulator/%$(1).x86_64.o: %.m $(EXTRA_DEPENDENCIES) | .libs/watchsimulator
+	$$(call Q_2,OBJC,  [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH64_OBJC_CFLAGS) $$(EXTRA_DEFINES) $(SIMW64_I) -g $(2) -c $$< -o $$@
+
+.libs/watchsimulator/%$(1).x86_64.o: %.c $(EXTRA_DEPENDENCIES) | .libs/watchsimulator
+	$$(call Q_2,CC,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH64_CFLAGS)      $$(EXTRA_DEFINES) $(SIMW64_I) -g $(2) -c $$< -o $$@
+
+.libs/watchsimulator/%$(1).x86_64.o: %.s $(EXTRA_DEPENDENCIES) | .libs/watchsimulator
+	$$(call Q_2,ASM,   [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH64_CFLAGS)      $$(EXTRA_DEFINES) $(SIMW64_I) -g $(2) -c $$< -o $$@
+
+.libs/watchsimulator/%$(1).x86_64.dylib: | .libs/watchsimulator
+	$$(call Q_2,LD,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH64_CFLAGS)      $$(EXTRA_FLAGS) -dynamiclib -o $$@ $$^ -L$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/lib -fapplication-extension
+
+.libs/watchsimulator/%$(1).x86_64.framework: | .libs/watchsimulator
+	$$(call Q_2,LD,    [watchsimulator]) $(SIMULATOR_CC) $(SIMULATORWATCH64_CFLAGS)      $$(EXTRA_FLAGS) -dynamiclib -o $$@ $$^ -F$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/Frameworks -fapplication-extension
 
 ## watch device
 
diff --git a/runtime/Makefile b/runtime/Makefile
index e9251a844202..b54c0d024a55 100644
--- a/runtime/Makefile
+++ b/runtime/Makefile
@@ -185,7 +185,7 @@ ifdef INCLUDE_WATCH
 ifdef INCLUDE_DEVICE
 $(eval $(call PlatformTemplate,watchos,WATCHOS,armv7k arm64_32))
 endif
-$(eval $(call PlatformTemplate,watchsimulator,WATCHSIMULATOR,x86))
+$(eval $(call PlatformTemplate,watchsimulator,WATCHSIMULATOR,x86 x86_64))
 endif
 
 ifdef INCLUDE_TVOS
@@ -565,6 +565,7 @@ $(eval $(call DotNetCopyLibTemplate,tvOS,tvos-arm64,tvos,arm64))
 endif
 endif
 ifdef INCLUDE_WATCH
+$(eval $(call DotNetCopyLibTemplate,watchOS,watchos-x64,watchsimulator,x86_64))
 $(eval $(call DotNetCopyLibTemplate,watchOS,watchos-x86,watchsimulator,i386))
 ifdef INCLUDE_DEVICE
 $(eval $(call DotNetLipoLibTemplate,watchOS,watchos-arm,watchos,armv7k arm64_32))
@@ -621,6 +622,7 @@ $(eval $(call DotNetCopyFrameworkTemplate,tvOS,tvos-arm64,tvos,arm64,$(IOS_DESTD
 endif
 endif
 ifdef INCLUDE_WATCH
+$(eval $(call DotNetCopyFrameworkTemplate,watchOS,watchos-x64,watchsimulator,x86_64,$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/Frameworks))
 $(eval $(call DotNetCopyFrameworkTemplate,watchOS,watchos-x86,watchsimulator,i386,$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/Frameworks))
 ifdef INCLUDE_DEVICE
 $(eval $(call DotNetLipoFrameworkTemplate,watchOS,watchos-arm,watchos,armv7k arm64_32,$(IOS_DESTDIR)$(XAMARIN_WATCHOS_SDK)/Frameworks))
diff --git a/src/Makefile b/src/Makefile
index b00381e63604..183f0080db20 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -808,11 +808,10 @@ $(WATCHOS_DOTNET_BUILD_DIR)/watchos.rsp: Makefile Makefile.generator frameworks.
 		$(WATCHOS_APIS) \
 		> $@
 
-$(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS%dll $(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS%pdb $(WATCHOS_DOTNET_BUILD_DIR)/ref/Xamarin.WatchOS%dll: $(WATCHOS_DOTNET_BUILD_DIR)/watchos-generated-sources $(WATCHOS_SOURCES) $(PRODUCT_KEY_PATH) | $(WATCHOS_DOTNET_BUILD_DIR)/32 $(WATCHOS_DOTNET_BUILD_DIR)/ref
+$(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS%dll $(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS%pdb: $(WATCHOS_DOTNET_BUILD_DIR)/watchos-generated-sources $(WATCHOS_SOURCES) $(PRODUCT_KEY_PATH) | $(WATCHOS_DOTNET_BUILD_DIR)/32 $(WATCHOS_DOTNET_BUILD_DIR)/ref
 	$(Q_DOTNET_GEN) \
 		$(SYSTEM_CSC) $(DOTNET_FLAGS) -out:$(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS.dll -optimize \
 		-publicsign -keyfile:$(PRODUCT_KEY_PATH) \
-		-refout:$(WATCHOS_DOTNET_BUILD_DIR)/ref/Xamarin.WatchOS.dll \
 		$(WATCH_DEFINES) \
 		$(ARGS_32) \
 		$(WATCHOS_WARNINGS_TO_FIX) \
@@ -821,6 +820,19 @@ $(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS%dll $(WATCHOS_DOTNET_BUILD_DIR)/3
 		$(WATCHOS_SOURCES) \
 		@$<
 
+$(WATCHOS_DOTNET_BUILD_DIR)/64/Xamarin.WatchOS%dll $(WATCHOS_DOTNET_BUILD_DIR)/64/Xamarin.WatchOS%pdb $(WATCHOS_DOTNET_BUILD_DIR)/ref/Xamarin.WatchOS%dll: $(WATCHOS_DOTNET_BUILD_DIR)/watchos-generated-sources $(WATCHOS_SOURCES) $(PRODUCT_KEY_PATH) | $(WATCHOS_DOTNET_BUILD_DIR)/64 $(WATCHOS_DOTNET_BUILD_DIR)/ref
+	$(Q_DOTNET_GEN) \
+		$(SYSTEM_CSC) $(DOTNET_FLAGS) -out:$(WATCHOS_DOTNET_BUILD_DIR)/64/Xamarin.WatchOS.dll -optimize \
+		-publicsign -keyfile:$(PRODUCT_KEY_PATH) \
+		-refout:$(WATCHOS_DOTNET_BUILD_DIR)/ref/Xamarin.WatchOS.dll \
+		$(WATCH_DEFINES) \
+		$(ARGS_64) \
+		$(WATCHOS_WARNINGS_TO_FIX) \
+		-warnaserror:$(NULLABILITY_WARNINGS) \
+		$(IOS_CSC_FLAGS_XI) \
+		$(WATCHOS_SOURCES) \
+		@$<
+
 $(WATCH_BUILD_DIR)/watch-32/Xamarin.WatchOS%dll $(WATCH_BUILD_DIR)/watch-32/Xamarin.WatchOS%pdb: $(WATCHOS_SOURCES) $(WATCH_BUILD_DIR)/watch/generated_sources $(PRODUCT_KEY_PATH) | $(WATCH_BUILD_DIR)/watch-32
 	$(call Q_PROF_CSC,watch) $(WATCH_CSC) -nologo -out:$(basename $@).dll -target:library -debug -unsafe -optimize \
 		-publicsign -keyfile:$(PRODUCT_KEY_PATH) $(WATCH_DEFINES) \
@@ -829,6 +841,14 @@ $(WATCH_BUILD_DIR)/watch-32/Xamarin.WatchOS%dll $(WATCH_BUILD_DIR)/watch-32/Xama
 		-nowarn:219,618,114,414,1635,3021,$(IOS_WARNINGS_THAT_YOU_SHOULD_FIX) \
 		$(WATCHOS_SOURCES) @$(WATCH_BUILD_DIR)/watch/generated_sources
 
+$(WATCH_BUILD_DIR)/watch-64/Xamarin.WatchOS%dll $(WATCH_BUILD_DIR)/watch-64/Xamarin.WatchOS%pdb: $(WATCHOS_SOURCES) $(WATCH_BUILD_DIR)/watch/generated_sources $(PRODUCT_KEY_PATH) | $(WATCH_BUILD_DIR)/watch-64
+	$(call Q_PROF_CSC,watch) $(WATCH_CSC) -nologo -out:$(basename $@).dll -target:library -debug -unsafe -optimize \
+		-publicsign -keyfile:$(PRODUCT_KEY_PATH) $(WATCH_DEFINES) \
+		-deterministic \
+		$(ARGS_64) \
+		-nowarn:219,618,114,414,1635,3021,$(IOS_WARNINGS_THAT_YOU_SHOULD_FIX) \
+		$(WATCHOS_SOURCES) @$(WATCH_BUILD_DIR)/watch/generated_sources
+
 $(WATCH_BUILD_DIR)/reference/Xamarin.WatchOS.dll: $(WATCH_BUILD_DIR)/watch-32/Xamarin.WatchOS.dll | $(WATCH_BUILD_DIR)/reference
 	$(Q_STRIP) mono-cil-strip -q $< $@
 
@@ -862,6 +882,7 @@ WATCH_TARGETS_DIRS +=                                          \
 	$(WATCH_BUILD_DIR)                                         \
 	$(WATCH_BUILD_DIR)/watch                                   \
 	$(WATCH_BUILD_DIR)/watch-32                                \
+	$(WATCH_BUILD_DIR)/watch-64                                \
 	$(WATCH_BUILD_DIR)/reference                               \
 	$(WATCH_BUILD_DIR)/reference/Facades                       \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/Xamarin.WatchOS \
@@ -873,12 +894,15 @@ WATCH_TARGETS += \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/Xamarin.WatchOS/Xamarin.WatchOS.dll          \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/Xamarin.WatchOS/Xamarin.WatchOS.pdb      \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/32bits/Xamarin.WatchOS.dll                        \
+	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/64bits/Xamarin.WatchOS.dll                        \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/32bits/Xamarin.WatchOS.pdb                    \
+	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/64bits/Xamarin.WatchOS.pdb                    \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/Xamarin.WatchOS/MonoTouch.NUnitLite.dll      \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mono/Xamarin.WatchOS/MonoTouch.NUnitLite.pdb
 
 DOTNET_TARGETS += \
 	$(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS.dll \
+	$(WATCHOS_DOTNET_BUILD_DIR)/64/Xamarin.WatchOS.dll \
 	$(WATCHOS_DOTNET_BUILD_DIR)/ref/Xamarin.WatchOS.dll \
 	$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Ref/ref/net5.0/Xamarin.WatchOS.dll \
 	$(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0/Xamarin.WatchOS.dll) \
@@ -888,6 +912,7 @@ DOTNET_TARGETS_DIRS += \
 	$(WATCHOS_DOTNET_BUILD_DIR) \
 	$(WATCHOS_DOTNET_BUILD_DIR)/generated-sources \
 	$(WATCHOS_DOTNET_BUILD_DIR)/32 \
+	$(WATCHOS_DOTNET_BUILD_DIR)/64 \
 	$(WATCHOS_DOTNET_BUILD_DIR)/ref \
 	$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Ref/ref/net5.0 \
 	$(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0) \
@@ -909,15 +934,27 @@ $(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Ref/ref/net5.0/Xamarin.WatchOS.dll: $(WATCHOS
 $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/32bits/Xamarin.WatchOS.dll: $(WATCH_BUILD_DIR)/watch-32/Xamarin.WatchOS.dll | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/32bits
 	$(Q) install -m 0755 $< $@
 
+$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/64bits/Xamarin.WatchOS.dll: $(WATCH_BUILD_DIR)/watch-64/Xamarin.WatchOS.dll | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/64bits
+	$(Q) install -m 0755 $< $@
+
 $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/32bits/Xamarin.WatchOS.pdb: $(WATCH_BUILD_DIR)/watch-32/Xamarin.WatchOS.pdb | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/32bits
 	$(Q) install -m 0644 $< $@
 
+$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/64bits/Xamarin.WatchOS.pdb: $(WATCH_BUILD_DIR)/watch-64/Xamarin.WatchOS.pdb | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/64bits
+	$(Q) install -m 0644 $< $@
+
 $(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_32),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0/Xamarin.WatchOS.dll): $(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS.dll | $(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_32),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0)
 	$(Q) $(CP) $< $@
 
+$(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_64),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0/Xamarin.WatchOS.dll): $(WATCHOS_DOTNET_BUILD_DIR)/64/Xamarin.WatchOS.dll | $(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_64),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0)
+	$(Q) $(CP) $< $@
+
 $(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_32),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0/Xamarin.WatchOS.pdb): $(WATCHOS_DOTNET_BUILD_DIR)/32/Xamarin.WatchOS.pdb | $(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_32),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0)
 	$(Q) $(CP) $< $@
 
+$(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_64),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0/Xamarin.WatchOS.pdb): $(WATCHOS_DOTNET_BUILD_DIR)/64/Xamarin.WatchOS.pdb | $(foreach rid,$(DOTNET_WATCHOS_RUNTIME_IDENTIFIERS_64),$(DOTNET_DESTDIR)/$(WATCHOS_NUGET).Runtime.$(rid)/runtimes/$(rid)/lib/net5.0)
+	$(Q) $(CP) $< $@
+
 $(WATCH_TARGETS_DIRS):
 	$(Q) mkdir -p $@
 
diff --git a/src/ObjCRuntime/Registrar.cs b/src/ObjCRuntime/Registrar.cs
index f7494e8f8765..d3b3ea96b0bc 100644
--- a/src/ObjCRuntime/Registrar.cs
+++ b/src/ObjCRuntime/Registrar.cs
@@ -838,7 +838,11 @@ public Trampoline Trampoline {
 					var mi = (System.Reflection.MethodInfo) Method;
 					bool is_stret;
 #if __WATCHOS__
-					is_stret = Runtime.Arch == Arch.DEVICE ? Stret.ArmNeedStret (NativeReturnType, null) : Stret.X86NeedStret (NativeReturnType, null);
+					if (Runtime.Arch == Arch.DEVICE) {
+						is_stret = Stret.ArmNeedStret (NativeReturnType, null);
+					} else {
+						is_stret = IntPtr.Size == 4 ? Stret.X86NeedStret (NativeReturnType, null) : Stret.X86_64NeedStret (NativeReturnType, null);
+					}
 #elif MONOMAC
 					is_stret = IntPtr.Size == 8 ? Stret.X86_64NeedStret (NativeReturnType, null) : Stret.X86NeedStret (NativeReturnType, null);
 #elif __IOS__
diff --git a/tests/bcl-test/watchOS-monotouch_Microsoft.CSharp_xunit-test.dll.ignore b/tests/bcl-test/watchOS-monotouch_Microsoft.CSharp_xunit-test.dll.ignore
index 3ba1ac79e4b9..deafac9925c8 100644
--- a/tests/bcl-test/watchOS-monotouch_Microsoft.CSharp_xunit-test.dll.ignore
+++ b/tests/bcl-test/watchOS-monotouch_Microsoft.CSharp_xunit-test.dll.ignore
@@ -4,3 +4,150 @@ Microsoft.CSharp.RuntimeBinder.Tests.DefaultParameterTests.MarshalAsOptionalsCor
 # System.NotImplementedException
 Microsoft.CSharp.RuntimeBinder.Tests.DelegateInDynamicTests.DelegateWithOutParametersInDynamicNamedArgumentInvocation
 Microsoft.CSharp.RuntimeBinder.Tests.DelegateInDynamicTests.DelegateWithOutParameterInDynamic
+
+# Service exited due to SIGFPE
+# https://github.com/mono/mono/issues/20632
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: -9223372036854775808)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 18446744073709551615)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 4294967295)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: -2147483648)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 4294967295)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 18446744073709551615)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: -9223372036854775808)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Modulo, x: -2147483648)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideByZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 18446744073709551615)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 4294967295)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 18446744073709551615)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: -9223372036854775808)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: -2147483648)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 4294967295)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: -9223372036854775808)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: -2147483648)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.DivideByConstantZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantModuloSignedMinimumByMinusOne(dividend: -9223372036854775808, divisor: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantModuloSignedMinimumByMinusOne(dividend: -2147483648, divisor: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 18446744073709551615)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 4294967295)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: -9223372036854775808)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: -9223372036854775808)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: -2147483648)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 2147483647)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 4294967295)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 3)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 0)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 9223372036854775807)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Divide, x: 1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: 18446744073709551615)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideByZero(type: Modulo, x: -2147483648)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.IntegerDivideByLiteralZero
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideSignedMinimumByMinusOne(dividend: -9223372036854775808, divisor: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.ConstantDivideSignedMinimumByMinusOne(dividend: -2147483648, divisor: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.IntegeryDivideByConstZero
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideSignedMinimumByMinusOne(type: Modulo, dividend: -2147483648, divisor: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideSignedMinimumByMinusOne(type: Divide, dividend: -9223372036854775808, divisor: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideSignedMinimumByMinusOne(type: Modulo, dividend: -9223372036854775808, divisor: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.RuntimeDivideSignedMinimumByMinusOne(type: Divide, dividend: -2147483648, divisor: -1)
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.NullDMO
+Microsoft.CSharp.RuntimeBinder.Tests.IntegerBinaryOperationTests.IntegeryDivideByLocalZero
diff --git a/tests/bcl-test/watchOS-monotouch_Mono.Runtime.Tests_test.dll.ignore b/tests/bcl-test/watchOS-monotouch_Mono.Runtime.Tests_test.dll.ignore
new file mode 100644
index 000000000000..26695e41b26e
--- /dev/null
+++ b/tests/bcl-test/watchOS-monotouch_Mono.Runtime.Tests_test.dll.ignore
@@ -0,0 +1,3 @@
+# tracked DivideByZeroException / Service exited due to SIGFPE
+# https://github.com/mono/mono/issues/20632
+MonoTests.Runtime.JitTests.Exceptions
diff --git a/tests/bcl-test/watchOS-monotouch_System.Core_xunit-test.dll.ignore b/tests/bcl-test/watchOS-monotouch_System.Core_xunit-test.dll.ignore
new file mode 100644
index 000000000000..b6d8b8fe4e25
--- /dev/null
+++ b/tests/bcl-test/watchOS-monotouch_System.Core_xunit-test.dll.ignore
@@ -0,0 +1,13 @@
+# Service exited due to SIGFPE
+# https://github.com/mono/mono/issues/20632
+KLASS:System.Linq.Expressions.Tests.LambdaDivideTests
+KLASS:System.Linq.Expressions.Tests.LiftedModuloNullableTests
+KLASS:System.Linq.Expressions.Tests.BinaryDivideTests
+KLASS:System.Linq.Expressions.Tests.LiftedDivideNullableTests
+KLASS:System.Linq.Expressions.Tests.LambdaModuloTests
+KLASS:System.Linq.Expressions.Tests.BinaryNullableDivideTests
+KLASS:System.Linq.Expressions.Tests.LambdaModuloNullableTests
+KLASS:System.Linq.Expressions.Tests.LambdaDivideNullableTests
+KLASS:System.Linq.Expressions.Tests.BinaryNullableModuloTests
+KLASS:System.Linq.Expressions.Tests.BinaryModuloTests
+KLASS:System.Dynamic.Tests.BinaryOperationTests
diff --git a/tests/bcl-test/watchOS-monotouch_System.Numerics_test.dll.ignore b/tests/bcl-test/watchOS-monotouch_System.Numerics_test.dll.ignore
new file mode 100644
index 000000000000..52ac8dd8c7ed
--- /dev/null
+++ b/tests/bcl-test/watchOS-monotouch_System.Numerics_test.dll.ignore
@@ -0,0 +1,4 @@
+# DivideByZeroException / Service exited due to SIGFPE
+# https://github.com/mono/mono/issues/20632
+MonoTests.System.Numerics.BigIntegerTest.DivRemByZero
+MonoTests.System.Numerics.BigIntegerTest.ModPow
diff --git a/tests/bcl-test/watchOS-monotouch_System.Numerics_xunit-test.dll.ignore b/tests/bcl-test/watchOS-monotouch_System.Numerics_xunit-test.dll.ignore
new file mode 100644
index 000000000000..c89d1b165380
--- /dev/null
+++ b/tests/bcl-test/watchOS-monotouch_System.Numerics_xunit-test.dll.ignore
@@ -0,0 +1,15 @@
+# DivideByZeroException / Service exited due to SIGFPE
+# https://github.com/mono/mono/issues/20632
+KLASS:System.Numerics.Tests.divremTest
+KLASS:System.Numerics.Tests.DivideTest
+KLASS:System.Numerics.Tests.propertiesTest
+System.Numerics.Tests.op_modulusTest.RunRemainderNegative
+System.Numerics.Tests.remainderTest.RunRemainderNegative
+System.Numerics.Tests.op_divideTest.RunDivideNegative
+System.Numerics.Tests.modpowTest.ModPowNegative
+System.Numerics.Tests.GenericVectorTests.DivisionByZeroExceptionInt16
+System.Numerics.Tests.GenericVectorTests.DivisionByZeroExceptionUInt16
+System.Numerics.Tests.GenericVectorTests.DivisionByZeroExceptionInt32
+System.Numerics.Tests.GenericVectorTests.DivisionByZeroExceptionByte
+System.Numerics.Tests.GenericVectorTests.DivisionByZeroExceptionSByte
+System.Numerics.Tests.GenericVectorTests.DivisionByZeroExceptionInt64
diff --git a/tests/mtouch/MTouch.cs b/tests/mtouch/MTouch.cs
index d049f02fdb33..cb5e349333bd 100644
--- a/tests/mtouch/MTouch.cs
+++ b/tests/mtouch/MTouch.cs
@@ -2528,6 +2528,7 @@ public void Architectures_TVOS_Invalid ()
 		[TestCase (Target.Dev, "arm64_32+llvm", "ARM64_32", MTouchBitcode.Unspecified)]
 		[TestCase (Target.Dev, "armv7k+llvm,arm64_32+llvm", "ARMv7k,ARM64_32", MTouchBitcode.Full)]
 		[TestCase (Target.Sim, null, "i386", MTouchBitcode.Unspecified)]
+		[TestCase (Target.Sim, "x86_64", "x86_64", MTouchBitcode.Unspecified)]
 		public void Architectures_WatchOS (Target target, string abi, string expected_abi, MTouchBitcode bitcode)
 		{
 			AssertDeviceAvailable ();
diff --git a/tests/test-libraries/Makefile b/tests/test-libraries/Makefile
index 07f96f7a6e16..7247373fac6a 100644
--- a/tests/test-libraries/Makefile
+++ b/tests/test-libraries/Makefile
@@ -124,7 +124,7 @@ $(eval $(call Template,tvsimulator,TVSIMULATOR,x86_64,AppleTVSimulator,-mtvos-si
 $(eval $(call Template,tvos,TVOS,arm64,AppleTVOS,-mtvos-version-min=9.0 -fembed-bitcode,TVOS))
 endif
 ifdef INCLUDE_WATCH
-$(eval $(call Template,watchsimulator,WATCHSIMULATOR,x86,WatchSimulator,-mwatchos-simulator-version-min=2.0,WATCHOS))
+$(eval $(call Template,watchsimulator,WATCHSIMULATOR,x86 x86_64,WatchSimulator,-mwatchos-simulator-version-min=2.0,WATCHOS))
 $(eval $(call Template,watchos,WATCHOS,armv7k arm64_32,WatchOS,-mwatchos-version-min=2.0 -fembed-bitcode,WATCHOS))
 endif
 ifdef INCLUDE_MAC
diff --git a/tests/xharness/Jenkins/Jenkins.cs b/tests/xharness/Jenkins/Jenkins.cs
index 412af62b6525..9a90fc9ddc90 100644
--- a/tests/xharness/Jenkins/Jenkins.cs
+++ b/tests/xharness/Jenkins/Jenkins.cs
@@ -42,7 +42,7 @@ class Jenkins {
 		public bool IncludeiOSExtensions;
 		public bool ForceExtensionBuildOnly;
 		public bool IncludetvOS = true;
-		public bool IncludewatchOS = false;
+		public bool IncludewatchOS = true;
 		public bool IncludeMmpTest;
 		public bool IncludeiOSMSBuild = true;
 		public bool IncludeMtouch;
diff --git a/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/Resources/Managed.watchOS.App.csproj.in b/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/Resources/Managed.watchOS.App.csproj.in
index a5da7b00d80b..f24c95f38b83 100644
--- a/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/Resources/Managed.watchOS.App.csproj.in
+++ b/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/Resources/Managed.watchOS.App.csproj.in
@@ -21,7 +21,7 @@
     <DefineConstants>DEBUG;</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
-    <MtouchArch>i386</MtouchArch>
+    <MtouchArch>i386, x86_64</MtouchArch>
     <MtouchLink>None</MtouchLink>
     <MtouchFastDev>true</MtouchFastDev>
     <MtouchDebug>true</MtouchDebug>
@@ -46,7 +46,7 @@
     <Optimize>true</Optimize>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
-    <MtouchArch>i386</MtouchArch>
+    <MtouchArch>i386, x86_64</MtouchArch>
     <MtouchLink>None</MtouchLink>
     <CodesignKey>iPhone Developer</CodesignKey>
   </PropertyGroup>
diff --git a/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/Resources/Managed.watchOS.Extension.csproj.in b/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/Resources/Managed.watchOS.Extension.csproj.in
index 10fc91f4201d..d6a0a6b82130 100644
--- a/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/Resources/Managed.watchOS.Extension.csproj.in
+++ b/tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/Resources/Managed.watchOS.Extension.csproj.in
@@ -27,7 +27,7 @@
     <MtouchDebug>True</MtouchDebug>
     <MtouchExtraArgs></MtouchExtraArgs>
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
-    <MtouchArch>i386</MtouchArch>
+    <MtouchArch>i386, x86_64</MtouchArch>
     <CodesignKey>iPhone Developer</CodesignKey>
     <MtouchLink>None</MtouchLink>
     <MtouchI18n>cjk,mideast,other,rare,west</MtouchI18n>
@@ -42,7 +42,7 @@
     <MtouchLink>None</MtouchLink>
     <MtouchExtraArgs></MtouchExtraArgs>
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
-    <MtouchArch>i386</MtouchArch>
+    <MtouchArch>i386, x86_64</MtouchArch>
     <MtouchI18n>cjk,mideast,other,rare,west</MtouchI18n>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|iPhone' ">
diff --git a/tests/xharness/Targets/WatchOSTarget.cs b/tests/xharness/Targets/WatchOSTarget.cs
index e4168a037874..68455089e2ed 100644
--- a/tests/xharness/Targets/WatchOSTarget.cs
+++ b/tests/xharness/Targets/WatchOSTarget.cs
@@ -21,7 +21,7 @@ public class WatchOSTarget : iOSTarget
 		public string WatchOSProjectPath { get { return ProjectPath; } private set { ProjectPath = value; } }
 
 		public override string SimulatorArchitectures {
-			get { return "i386"; }
+			get { return "i386, x86_64"; }
 		}
 
 		public override string DeviceArchitectures {
diff --git a/tools/common/Application.cs b/tools/common/Application.cs
index c95d2e8457f7..a3a361179d00 100644
--- a/tools/common/Application.cs
+++ b/tools/common/Application.cs
@@ -671,6 +671,7 @@ public void ValidateAbi ()
 					validAbis.Add (Abi.ARM64_32 | Abi.LLVM);
 				} else {
 					validAbis.Add (Abi.i386);
+					validAbis.Add (Abi.x86_64);
 				}
 				break;
 			case ApplePlatform.TVOS:
diff --git a/tools/mtouch/Makefile b/tools/mtouch/Makefile
index 292597b83042..9135e71eff8e 100644
--- a/tools/mtouch/Makefile
+++ b/tools/mtouch/Makefile
@@ -237,6 +237,7 @@ $(eval $(call RunRegistrar,ios,armv7s,32,$(IOS_SDK_VERSION),iOS,$(DEVICE7S_CFLAG
 $(eval $(call RunRegistrar,ios,arm64,64,$(IOS_SDK_VERSION),iOS,$(DEVICE64_CFLAGS),$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/SDKs/MonoTouch.iphoneos.sdk/include,$(MONOTOUCH_MONO_PATH)))
 $(eval $(call RunRegistrar,tvos,x86_64,64,$(TVOS_SDK_VERSION),TVOS,$(SIMULATORTV_CFLAGS),$(IOS_DESTDIR)$(XAMARIN_TVSIMULATOR_SDK)/include,$(MONOTOUCH_TV_MONO_PATH)))
 $(eval $(call RunRegistrar,tvos,arm64,64,$(TVOS_SDK_VERSION),TVOS,$(DEVICETV_CFLAGS),$(IOS_DESTDIR)$(XAMARIN_TVOS_SDK)/include,$(MONOTOUCH_TV_MONO_PATH)))
+$(eval $(call RunRegistrar,watchos,x86_64,64,$(WATCH_SDK_VERSION),WatchOS,$(SIMULATORWATCH64_CFLAGS),$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/include,$(MONOTOUCH_WATCH_MONO_PATH)))
 $(eval $(call RunRegistrar,watchos,i386,32,$(WATCH_SDK_VERSION),WatchOS,$(SIMULATORWATCH_CFLAGS),$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/include,$(MONOTOUCH_WATCH_MONO_PATH)))
 $(eval $(call RunRegistrar,watchos,armv7k,32,$(WATCH_SDK_VERSION),WatchOS,$(DEVICEWATCH_CFLAGS),$(IOS_DESTDIR)$(XAMARIN_WATCHOS_SDK)/include,$(MONOTOUCH_WATCH_MONO_PATH)))
 $(eval $(call RunRegistrar,watchos,arm64_32,32,$(WATCH_SDK_VERSION),WatchOS,$(DEVICEWATCH64_32_CFLAGS),$(IOS_DESTDIR)$(XAMARIN_WATCHOS_SDK)/include,$(MONOTOUCH_WATCH_MONO_PATH)))
@@ -250,6 +251,9 @@ $(eval $(call RunRegistrar,watchos,arm64_32,32,$(WATCH_SDK_VERSION),WatchOS,$(DE
 %.registrar.watchos.device.a:    %.registrar.watchos.armv7k.a %.registrar.watchos.arm64_32.a
 	$(Q_LIPO) $(DEVICE_BIN_PATH)/lipo -create -output $@ $^
 
+%.registrar.watchos.simulator.a: %.registrar.watchos.i386.a %.registrar.watchos.x86_64.a
+	$(Q_LIPO) $(DEVICE_BIN_PATH)/lipo -create -output $@ $^
+
 TARGETS = \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/bin/mtouch                                          \
 	$(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/mtouch/mtouch.exe                               \
@@ -312,7 +316,7 @@ $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/lib/%: % | $(IOS_DESTDIR)$(MONOTOUCH_PREFIX)/l
 $(IOS_DESTDIR)$(MONOTOUCH_SIMULATOR_SDK)/lib/%.registrar.a: %.registrar.ios.simulator.a | $(IOS_DESTDIR)$(MONOTOUCH_SIMULATOR_SDK)/lib
 	$(Q) $(CP) $< $@
 
-$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/lib/%.registrar.a: %.registrar.watchos.i386.a | $(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/lib
+$(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/lib/%.registrar.a: %.registrar.watchos.simulator.a | $(IOS_DESTDIR)$(XAMARIN_WATCHSIMULATOR_SDK)/lib
 	$(Q) $(CP) $< $@
 
 $(IOS_DESTDIR)$(XAMARIN_TVSIMULATOR_SDK)/lib/%.registrar.a: %.registrar.tvos.x86_64.a | $(IOS_DESTDIR)$(XAMARIN_TVSIMULATOR_SDK)/lib
diff --git a/tools/mtouch/mtouch.cs b/tools/mtouch/mtouch.cs
index e5d50c06a297..6acf7050d0f7 100644
--- a/tools/mtouch/mtouch.cs
+++ b/tools/mtouch/mtouch.cs
@@ -161,6 +161,7 @@ public static string GetArch64Directory (Application app)
 			switch (app.Platform) {
 			case ApplePlatform.iOS:
 			case ApplePlatform.TVOS:
+			case ApplePlatform.WatchOS:
 				return Path.Combine (GetPlatformFrameworkDirectory (app), "..", "..", "64bits");
 			default:
 				throw ErrorHelper.CreateError (71, Errors.MX0071, app.Platform, "Xamarin.iOS");