diff --git a/lib/nimbase.h b/lib/nimbase.h
index 0e037cd311..ebc919b0b3 100644
--- a/lib/nimbase.h
+++ b/lib/nimbase.h
@@ -491,13 +491,22 @@ typedef char* NCSTRING;
 
 #define paramCount() cmdCount
 
-// NAN definition copied from math.h included in the Windows SDK version 10.0.14393.0
-#ifndef NAN
+#ifndef NAN  /* use __builtin_nanf which is faster, if available */
+#  if defined(__GNUC__)
+#    define NAN (__builtin_nanf(""))
+#  elif defined(__clang__) /* XXX: writing __has_builtin this line cause MSVC complains. */
+#    if __has_builtin (__builtin_nanf)
+#      define NAN (__builtin_nanf(""))
+#    endif
+#  endif
+#endif
+
+#ifndef NAN  /* modified from math.h included in the Windows SDK version 10.0.26100.0 */
 #  ifndef _HUGE_ENUF
-#    define _HUGE_ENUF  1e+300  // _HUGE_ENUF*_HUGE_ENUF must overflow
+#    define _HUGE_ENUF  1e+300  /* _HUGE_ENUF*_HUGE_ENUF must overflow */
 #  endif
 #  define NAN_INFINITY ((float)(_HUGE_ENUF * _HUGE_ENUF))
-#  define NAN ((float)(NAN_INFINITY * 0.0F))
+#  define NAN (-(float)(NAN_INFINITY * 0.0F))
 #endif
 
 #ifndef INF