diff --git a/mix.exs b/mix.exs
index c1ab1d7..e402409 100644
--- a/mix.exs
+++ b/mix.exs
@@ -16,8 +16,7 @@ use Mix.Project
   defp opts(:dev), do: [d: :TEST]
   defp opts(_), do: []
 
-  defp deps(:dev), do: [{:mixunit, "~> 0.9.1", [optional: true]}]
-  defp deps(_), do: []
+  defp deps(), do: [{:mixunit, "~> 0.9.1", [only: :dev]}]
 
   defp package do
     [