diff --git a/include/fpmath.h b/include/fpmath.h
index 49c44e5..7c4b02c 100644
--- a/include/fpmath.h
+++ b/include/fpmath.h
@@ -59,7 +59,7 @@
 #include <machine/endian.h>
 #endif
 
-#ifdef WIN32
+#ifdef __WIN32__
 #define _LITTLE_ENDIAN 1234
 #define _BIG_ENDIAN    4321
 #define _PDP_ENDIAN    3412