diff --git a/core/utils.c b/core/utils.c
index 57ef1bfb..c3be311d 100644
--- a/core/utils.c
+++ b/core/utils.c
@@ -2922,7 +2922,7 @@ size_t uwsgi_str_num(char *str, int len) {
 	int i;
 	size_t num = 0;
 
-	size_t delta = pow(10, len);
+	uint64_t delta = pow(10, len);
 
 	for (i = 0; i < len; i++) {
 		delta = delta / 10;