diff --git a/configure.in b/configure.in
index d36dccbcd..1bb3ea7a4 100644
--- a/configure.in
+++ b/configure.in
@@ -902,9 +902,6 @@ int main () { return (isinf(0.0) != 0); }],
 AC_MSG_CHECKING([for isnan])
 AC_LINK_IFELSE(
 [#include <math.h>
-#ifdef __MINGW32__
-#define isnan _isnan
-#endif
 int main () { return (isnan(0.0) != 0); }],
   [AC_MSG_RESULT([yes])
    AC_DEFINE(HAVE_ISNAN, 1,