diff --git a/lib/isc/url.c b/lib/isc/url.c
index 6ba4cb4991..e6a3b830ee 100644
--- a/lib/isc/url.c
+++ b/lib/isc/url.c
@@ -549,8 +549,8 @@ isc_url_parse(const char *buf, size_t buflen, bool is_connect,
 	int found_at = 0;
 	const char *p = NULL;
 
-	if (buflen == 0) {
-		return ISC_R_FAILURE;
+	if (buflen == 0 || buflen > UINT16_MAX) {
+		return ISC_R_RANGE;
 	}
 
 	up->port = up->field_set = 0;