diff --git a/mix.exs b/mix.exs
index bbc1139..5d75f9f 100644
--- a/mix.exs
+++ b/mix.exs
@@ -18,7 +18,7 @@ defmodule HttpSignatures.MixProject do
   # Run "mix help compile.app" to learn about applications.
   def application do
     [
-      extra_applications: [:logger]
+      extra_applications: [:logger, :public_key]
     ]
   end