diff --git a/src/rebar_relx.erl b/src/rebar_relx.erl
index c457b22d1..913fcb573 100644
--- a/src/rebar_relx.erl
+++ b/src/rebar_relx.erl
@@ -236,10 +236,14 @@ maybe_obey_command_args(RelxConfig, Opts, Args) ->
                      undefined ->
                          Acc;
                      V ->
-                         lists:keystore(Opt, 1, Acc, {Opt, V})
+                         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).
+
 %%
 
 %% Returns a map of all apps that are part of the rebar3 project.