diff --git a/mrbgems/mruby-complex/mrblib/complex.rb b/mrbgems/mruby-complex/mrblib/complex.rb
index 4c36179cb..e341efc5d 100644
--- a/mrbgems/mruby-complex/mrblib/complex.rb
+++ b/mrbgems/mruby-complex/mrblib/complex.rb
@@ -74,3 +74,9 @@ class Complex < Numeric
   end
   undef i
 end
+
+class Numeric
+  def to_c
+    Complex(self, 0)
+  end
+end