diff --git a/contrib/pg_upgrade/util.c b/contrib/pg_upgrade/util.c
index 8ee39be03ed..52b81c200b3 100644
--- a/contrib/pg_upgrade/util.c
+++ b/contrib/pg_upgrade/util.c
@@ -269,5 +269,5 @@ getErrorText(int errNum)
 unsigned int
 str2uint(const char *str)
 {
-	return strtol(str, NULL, 10);
+	return strtoul(str, NULL, 10);
 }