diff --git a/lib/bandit.ex b/lib/bandit.ex
index 2af488ef..d3cd8eae 100644
--- a/lib/bandit.ex
+++ b/lib/bandit.ex
@@ -293,7 +293,7 @@ defmodule Bandit do
         options
 
       {_, illegal_options} ->
-        raise "Unsupported keys(s) in #{name} config: #{inspect(Keyword.keys(illegal_options))}"
+        raise "Unsupported key(s) in #{name} config: #{inspect(Keyword.keys(illegal_options))}"
     end
   end