diff --git a/ext/yajl/extconf.rb b/ext/yajl/extconf.rb
index 439c0eb5..f0c7a00a 100644
--- a/ext/yajl/extconf.rb
+++ b/ext/yajl/extconf.rb
@@ -1,7 +1,7 @@
 require 'mkmf'
 require 'rbconfig'
 
-$CFLAGS << ' -Wall -funroll-loops'
-$CFLAGS << ' -Wextra -O0 -ggdb3' if ENV['DEBUG']
+$CFLAGS << ' -Wall -funroll-loops' unless $mswin
+$CFLAGS << ' -Wextra -O0 -ggdb3' if ENV['DEBUG'] && !$mswin
 
 create_makefile('yajl/yajl')