diff --git a/rebar.config b/rebar.config
index 0562dd96e..92a604f8b 100644
--- a/rebar.config
+++ b/rebar.config
@@ -7,7 +7,7 @@
         {providers,        "1.9.0"},
         {getopt,           "1.0.1"},
         {bbmustache,       "1.12.2"},
-        {relx,             "4.5.0"},
+        {relx,             "4.6.0"},
         {cf,               "0.3.1"},
         {cth_readable,     "1.5.1"},
         {eunit_formatters, "0.5.0"}]}.
diff --git a/rebar.lock b/rebar.lock
index ed23ddfb3..bc5d0ce5d 100644
--- a/rebar.lock
+++ b/rebar.lock
@@ -7,7 +7,7 @@
  {<<"eunit_formatters">>,{pkg,<<"eunit_formatters">>,<<"0.5.0">>},0},
  {<<"getopt">>,{pkg,<<"getopt">>,<<"1.0.1">>},0},
  {<<"providers">>,{pkg,<<"providers">>,<<"1.9.0">>},0},
- {<<"relx">>,{pkg,<<"relx">>,<<"4.5.0">>},0},
+ {<<"relx">>,{pkg,<<"relx">>,<<"4.6.0">>},0},
  {<<"ssl_verify_fun">>,{pkg,<<"ssl_verify_fun">>,<<"1.1.6">>},0}]}.
 [
 {pkg_hash,[
@@ -19,7 +19,7 @@
  {<<"eunit_formatters">>, <<"6A9133943D36A465D804C1C5B6E6839030434B8879C5600D7DDB5B3BAD4CCB59">>},
  {<<"getopt">>, <<"C73A9FA687B217F2FF79F68A3B637711BB1936E712B521D8CE466B29CBF7808A">>},
  {<<"providers">>, <<"46F6645B0C677B1029E02B013BFD69092A2232854DAF359F2378FA42AC0BEC0D">>},
- {<<"relx">>, <<"2BF90A855023023EDD000641033D1AB9F4EBD4314D1739F691E16FE03CB35B85">>},
+ {<<"relx">>, <<"939DB831A63CC35A7850C99DCC758FE9F3900E32E1DAB7CBB34E5306CAF53168">>},
  {<<"ssl_verify_fun">>, <<"CF344F5692C82D2CD7554F5EC8FD961548D4FD09E7D22F5B62482E5AEAEBD4B0">>}]},
 {pkg_hash_ext,[
  {<<"bbmustache">>, <<"688B33A4D5CC2D51F575ADF0B3683FC40A38314A2F150906EDCFC77F5B577B3B">>},
@@ -30,6 +30,6 @@
  {<<"eunit_formatters">>, <<"D6C8BA213424944E6E05BBC097C32001CDD0ABE3925D02454F229B20D68763C9">>},
  {<<"getopt">>, <<"53E1AB83B9CEB65C9672D3E7A35B8092E9BDC9B3EE80721471A161C10C59959C">>},
  {<<"providers">>, <<"D287E874406A1505608642B0A3DB5B68D6ADA3F2AB001AEC87E7F4D7C79FC017">>},
- {<<"relx">>, <<"DDB58F20CCE6CA63F5A2725E925816DD7213476698A3F3C3CB4FA8C272202C52">>},
+ {<<"relx">>, <<"2FF8131C63093C621C6B37DC52D1B2848A938886584B4B701D35BDBE4377F509">>},
  {<<"ssl_verify_fun">>, <<"BDB0D2471F453C88FF3908E7686F86F9BE327D065CC1EC16FA4540197EA04680">>}]}
 ].
diff --git a/src/rebar_app_discover.erl b/src/rebar_app_discover.erl
index 1543b5b67..3700e81c2 100644
--- a/src/rebar_app_discover.erl
+++ b/src/rebar_app_discover.erl
@@ -415,6 +415,7 @@ create_app_info(AppInfo, AppDir, AppFile) ->
             AppVsn = proplists:get_value(vsn, AppDetails),
             Applications = proplists:get_value(applications, AppDetails, []),
             IncludedApplications = proplists:get_value(included_applications, AppDetails, []),
+            OptionalApplications = proplists:get_value(optional_applications, AppDetails, []),
             AppInfo1 = rebar_app_info:name(
                          rebar_app_info:vsn(
                            rebar_app_info:original_vsn(
@@ -422,14 +423,15 @@ create_app_info(AppInfo, AppDir, AppFile) ->
             AppInfo2 = rebar_app_info:applications(
                          rebar_app_info:app_details(AppInfo1, AppDetails), Applications),
             AppInfo3 = rebar_app_info:included_applications(AppInfo2, IncludedApplications),
-            Valid = case rebar_app_utils:validate_application_info(AppInfo3) =:= true
-                        andalso rebar_app_info:has_all_artifacts(AppInfo3) =:= true of
+            AppInfo4 = rebar_app_info:optional_applications(AppInfo3, OptionalApplications),
+            Valid = case rebar_app_utils:validate_application_info(AppInfo4) =:= true
+                        andalso rebar_app_info:has_all_artifacts(AppInfo4) =:= true of
                         true ->
                             true;
                         _ ->
                             false
                     end,
-            rebar_app_info:dir(rebar_app_info:valid(AppInfo3, Valid), AppDir);
+            rebar_app_info:dir(rebar_app_info:valid(AppInfo4, Valid), AppDir);
         _Invalid ->
             throw({error, {?MODULE, {cannot_read_app_file, AppFile}}})
     catch
diff --git a/src/rebar_app_info.erl b/src/rebar_app_info.erl
index ae43a1ff2..4f78f4312 100644
--- a/src/rebar_app_info.erl
+++ b/src/rebar_app_info.erl
@@ -32,6 +32,8 @@
          applications/2,
          included_applications/1,
          included_applications/2,
+         optional_applications/1,
+         optional_applications/2,
          profiles/1,
          profiles/2,
          deps/1,
@@ -94,6 +96,7 @@
                      app_details=[]     :: list(),
                      applications=[]    :: list(),
                      included_applications=[] :: [atom()],
+                     optional_applications=[] :: [atom()],
                      deps=[]            :: list(),
                      profiles=[default] :: [atom()],
                      default=dict:new() :: rebar_dict(),
@@ -181,6 +184,7 @@ new(Parent, AppName, Vsn, Dir, Deps) ->
                            vsn := app_vsn(),
                            applications := [atom()],
                            included_applications := [atom()],
+                           optional_applications := [atom()],
                            dir := file:name(),
                            out_dir := file:name(),
                            ebin_dir := file:name(),
@@ -189,12 +193,14 @@ app_to_map(#app_info_t{name=Name,
                        vsn=Vsn,
                        applications=Applications,
                        included_applications=IncludedApplications,
+                       optional_applications=OptionalApplications,
                        out_dir=OutDir,
                        ebin_dir=EbinDir}) ->
     #{name => ec_cnv:to_atom(Name),
       vsn => Vsn,
       applications => Applications,
       included_applications => IncludedApplications,
+      optional_applications => OptionalApplications,
       dir => OutDir,
       out_dir => OutDir,
       ebin_dir => EbinDir,
@@ -468,6 +474,17 @@ included_applications(#app_info_t{included_applications=Applications}) ->
 included_applications(AppInfo=#app_info_t{}, Applications) ->
     AppInfo#app_info_t{included_applications=Applications}.
 
+%% @doc returns the list of optional_applications the app depends on.
+-spec optional_applications(t()) -> list().
+optional_applications(#app_info_t{optional_applications=Applications}) ->
+    Applications.
+
+%% @doc sets the list of optional applications the app depends on.
+%% Should be obtained from the app file.
+-spec optional_applications(t(), list()) -> t().
+optional_applications(AppInfo=#app_info_t{}, Applications) ->
+    AppInfo#app_info_t{optional_applications=Applications}.
+
 %% @doc returns the list of active profiles
 -spec profiles(t()) -> list().
 profiles(#app_info_t{profiles=Profiles}) ->
diff --git a/src/rebar_relx.erl b/src/rebar_relx.erl
index bfe5cba5b..c457b22d1 100644
--- a/src/rebar_relx.erl
+++ b/src/rebar_relx.erl
@@ -262,9 +262,10 @@ app_info_to_relx(#{name := Name,
                    vsn := Vsn,
                    applications := Applications,
                    included_applications := IncludedApplications,
+                   optional_applications := OptionalApplications,
                    dir := Dir,
                    link := false}, AppType) ->
-    rlx_app_info:new(Name, Vsn, Dir, Applications, IncludedApplications, AppType).
+    rlx_app_info:new(Name, Vsn, Dir, Applications, IncludedApplications, OptionalApplications, AppType).
 
 -spec opt_spec_list() -> [getopt:option_spec()].
 opt_spec_list() ->