diff --git a/ext/standard/math.c b/ext/standard/math.c
index 62bf1a4b937..137b228d964 100644
--- a/ext/standard/math.c
+++ b/ext/standard/math.c
@@ -1011,7 +1011,7 @@ PHPAPI char *_php_math_number_format(double d, int dec, char dec_point, char tho
 
 	/* allow for thousand separators */
 	if (thousand_sep) {
-		integral += integral / 3;
+		integral += (integral-1) / 3;
 	}
 	
 	reslen = integral;