diff --git a/ext/date/extconf.rb b/ext/date/extconf.rb
index 9f7d3e8f0b..a8c6fcaab2 100644
--- a/ext/date/extconf.rb
+++ b/ext/date/extconf.rb
@@ -1,2 +1,3 @@
 require 'mkmf'
+config_string("strict_warnflags") {|w| $warnflags += " #{w}"}
 create_makefile('date_core')