diff --git a/ext/standard/math.c b/ext/standard/math.c
index cfaa7ae964e..f108e4f34d1 100644
--- a/ext/standard/math.c
+++ b/ext/standard/math.c
@@ -34,7 +34,6 @@
 #ifdef PHP_WIN32
 # define zend_finite(x) _finite(x)
 # define zend_isnan(x) _isnan(x)
-# define zend_isinf(x) _isnan(x)
 #endif
 
 /* {{{ proto int abs(int number)