diff --git i/win32/include/math.h w/win32/include/math.h
index 984a717..5f21cd0 100644
--- i/win32/include/math.h
+++ w/win32/include/math.h
@@ -693,6 +693,7 @@ extern "C" {
 	"fnstsw;": "=a" (retval) : "t" (x), "u" (y));
       return retval;
   }
+#define __fp_unordered_compare_DEFINED 1
 
 #define isgreater(x, y) ((__fp_unordered_compare(x, y) \
   & 0x4500) == 0)
@@ -749,6 +750,8 @@ extern "C++" {
 #define isunordered(x, y) __builtin_isunordered(x, y)
 
 #else
+
+#ifndef __fp_unordered_compare_DEFINED
 /*  helper  */
 __CRT_INLINE int  __cdecl
 __fp_unordered_compare (long double x, long double y){
@@ -757,6 +760,7 @@ __fp_unordered_compare (long double x, long double y){
 	   "fnstsw;": "=a" (retval) : "t" (x), "u" (y));
   return retval;
 }
+#endif
 
 #define isgreater(x, y) ((__fp_unordered_compare(x, y) \
 			   & 0x4500) == 0)