diff --git a/common.h b/common.h
index 3276951..12adfb3 100644
--- a/common.h
+++ b/common.h
@@ -26,12 +26,6 @@
 #ifndef _COMMON_H_
 #define _COMMON_H_
 
-#if defined(WIN32) || defined(_WIN32) || defined(_MSC_VER) || defined(__MINGW32__)
-#define _IS_WINDOWS
-#else
-#undef _IS_WINDOWS
-#endif
-
 /* MSVC starting include stdint.h fairly recently */
 #if !defined(_MSC_VER) || (MSC_VER >= 1800)
 # include <stdint.h>