diff --git a/lib/ruby2_keywords.rb b/lib/ruby2_keywords.rb
index 7516af3..855c9cb 100644
--- a/lib/ruby2_keywords.rb
+++ b/lib/ruby2_keywords.rb
@@ -13,3 +13,11 @@ def main.ruby2_keywords(*)
     # nil
   end
 end
+
+class Proc
+  unless method_defined?(:ruby2_keywords)
+    def ruby2_keywords
+      self
+    end
+  end
+end