diff --git a/source3/winbindd/idmap_autorid.c b/source3/winbindd/idmap_autorid.c
index fa16c1383a8..4669b8dba59 100644
--- a/source3/winbindd/idmap_autorid.c
+++ b/source3/winbindd/idmap_autorid.c
@@ -223,7 +223,7 @@ static NTSTATUS idmap_autorid_id_to_sid(struct autorid_global_config *cfg,
 		map->status = ID_UNKNOWN;
 		return NT_STATUS_OK;
 	}
-	if (q != NULL)
+	if ((q != NULL) && (*q != '\0'))
 		if (sscanf(q+1, "%"SCNu32, &domain_range_index) != 1) {
 			DEBUG(10, ("Domain range index not found, "
 				   "ignoring mapping request\n"));