diff --git a/build_tools/cmake/iree_python.cmake b/build_tools/cmake/iree_python.cmake
index 1b64c60f37ea..647bc1cd01fe 100644
--- a/build_tools/cmake/iree_python.cmake
+++ b/build_tools/cmake/iree_python.cmake
@@ -234,19 +234,25 @@ function(iree_local_py_test)
       ${_RULE_ARGS}
   )
 
-  list(APPEND _RULE_PACKAGE_DIRS "$ENV{PYTHONPATH}")
-  string(JOIN ":" _PYTHONPATH ${_RULE_PACKAGE_DIRS})
-
-  if (NOT DEFINED _RULE_TIMEOUT)
-    set(_RULE_TIMEOUT 60)
-  endif()
-
   set_property(TEST ${_NAME_PATH} PROPERTY LABELS "${_RULE_LABELS}")
   set_property(TEST ${_NAME_PATH} PROPERTY TIMEOUT ${_RULE_ARGS})
 
+  # Extend the PYTHONPATH environment variable with _RULE_PACKAGE_DIRS.
+  list(APPEND _RULE_PACKAGE_DIRS "$ENV{PYTHONPATH}")
+  if(${CMAKE_SYSTEM_NAME} STREQUAL "Windows")
+    # Windows uses semi-colon delimiters, but so does CMake, so escape them.
+    list(JOIN _RULE_PACKAGE_DIRS "\\;" _PYTHONPATH)
+  else()
+    list(JOIN _RULE_PACKAGE_DIRS ":" _PYTHONPATH)
+  endif()
   set_property(TEST ${_NAME_PATH} PROPERTY ENVIRONMENT
       "PYTHONPATH=${_PYTHONPATH}"
   )
+
+  if (NOT DEFINED _RULE_TIMEOUT)
+    set(_RULE_TIMEOUT 60)
+  endif()
+
   iree_configure_test(${_NAME_PATH})
 
   # TODO(marbre): Find out how to add deps to tests.
diff --git a/runtime/src/iree/builtins/ukernel/tools/pack_test.cc b/runtime/src/iree/builtins/ukernel/tools/pack_test.cc
index fef1dff2e8c8..fc3da46de7d3 100644
--- a/runtime/src/iree/builtins/ukernel/tools/pack_test.cc
+++ b/runtime/src/iree/builtins/ukernel/tools/pack_test.cc
@@ -173,7 +173,7 @@ static void pack_test(const iree_uk_pack_type_t& type) {
   for (const auto& shape : untransposed_out_shapes) {
     for (bool transpose_inner : {false, true}) {
       for (bool transpose_outer : {false, true}) {
-        iree_uk_pack_params_t params;
+        iree_uk_pack_params_t params = {};
         params.type = type;
         params.in_size0 = shape.size0 * shape.size2;
         params.in_size1 = shape.size1 * shape.size3;
diff --git a/samples/simple_embedding/BUILD b/samples/simple_embedding/BUILD
index 00725c390efd..7b26e0e00a6a 100644
--- a/samples/simple_embedding/BUILD
+++ b/samples/simple_embedding/BUILD
@@ -252,6 +252,9 @@ iree_bytecode_module(
 native_test(
     name = "simple_embedding_vulkan_test",
     src = ":simple_embedding_vulkan",
+    tags = [
+        "driver=vulkan",
+    ],
 )
 
 iree_cmake_extra_content(
diff --git a/samples/simple_embedding/CMakeLists.txt b/samples/simple_embedding/CMakeLists.txt
index 9a410001db08..8cbd4406bf10 100644
--- a/samples/simple_embedding/CMakeLists.txt
+++ b/samples/simple_embedding/CMakeLists.txt
@@ -243,6 +243,8 @@ iree_native_test(
     "simple_embedding_vulkan_test"
   SRC
     ::simple_embedding_vulkan
+  LABELS
+    "driver=vulkan"
 )
 
 endif()