diff --git a/src/stream.c b/src/stream.c
index 005b49eea..019d252f9 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -2942,12 +2942,12 @@ struct ist stream_generate_unique_id(struct stream *strm, struct lf_expr *format
 	}
 	else {
 		char *unique_id;
-		int length;
+
 		if ((unique_id = pool_alloc(pool_head_uniqueid)) == NULL)
 			return IST_NULL;
 
-		length = build_logline(strm, unique_id, UNIQUEID_LEN, format);
-		strm->unique_id = ist2(unique_id, length);
+		strm->unique_id = ist2(unique_id, 0);
+		strm->unique_id.len = build_logline(strm, unique_id, UNIQUEID_LEN, format);
 
 		return strm->unique_id;
 	}