diff --git a/apps/rebar/src/rebar_relx.erl b/apps/rebar/src/rebar_relx.erl
index bfb4674d0..5a20e12a3 100644
--- a/apps/rebar/src/rebar_relx.erl
+++ b/apps/rebar/src/rebar_relx.erl
@@ -235,13 +235,16 @@ maybe_obey_command_args(RelxConfig, Opts, Args) ->
                      undefined ->
                          Acc;
                      V ->
-                         replace_all_instance(Opt, V, Acc)
+                         add_or_replace_all_instance(Opt, V, Acc)
                  end
         end, RelxConfig, Args).
 
-replace_all_instance(Opt, Value, RelxConfig) ->
-    lists:map(fun({K, _}) when K =:= Opt -> {K, Value};
-            (Other) -> Other end, RelxConfig).
+add_or_replace_all_instance(Opt, Value, RelxConfig) ->
+    case lists:keymember(Opt, 1, RelxConfig) of
+        true -> lists:map(fun({K, _}) when K =:= Opt -> {K, Value};
+                             (Other) -> Other end, RelxConfig);
+        false -> [{Opt, Value} | RelxConfig]
+    end.
 
 %%
 
diff --git a/apps/rebar/test/rebar_release_SUITE.erl b/apps/rebar/test/rebar_release_SUITE.erl
index a793317f3..dd6c33b1c 100644
--- a/apps/rebar/test/rebar_release_SUITE.erl
+++ b/apps/rebar/test/rebar_release_SUITE.erl
@@ -8,6 +8,7 @@ all() -> [release,
           dev_mode_release,
           profile_dev_mode_override_release,
           tar,
+          command_line_override,
           profile_ordering_sys_config_extend,
           profile_ordering_sys_config_extend_3_tuple_merge,
           extend_release,
@@ -74,6 +75,19 @@ config_file(Config) ->
     rebar_test_utils:run_and_check(Config, [{relx, RelxConfig("4.0.0")}], ["release"],
                                    {ok, [{release, Name, "4.0.0", false}]}).
 
+command_line_override(Config) ->
+    %% regression test for #2967
+    AppDir = ?config(apps, Config),
+    Vsn = "0.0.0",
+    Name = list_to_atom(?config(name, Config)),
+    Content = [{Name, [{something, true}]}],
+    InputPath = filename:join([AppDir, "config", "mysysconfig"]),
+    rebar_test_utils:create_config(AppDir, InputPath, Content),
+    RelxConfig = [{release, {Name, Vsn}, [Name]}, {lib_dirs, [AppDir]}],
+    rebar_test_utils:run_and_check(Config, [{relx, RelxConfig}], ["release", "--sys_config=" ++ InputPath],
+                                   {ok, [{release, Name, Vsn, false}]}),
+    {ok, Content} = file:consult(filename:join([AppDir, "_build/default/rel", Name, "releases", Vsn, "sys.config"])).
+
 dev_mode_release(Config) ->
     AppDir = ?config(apps, Config),
     Name = ?config(name, Config),