diff --git a/src/backup.c b/src/backup.c
index 83b311c4..57c4be51 100644
--- a/src/backup.c
+++ b/src/backup.c
@@ -547,7 +547,8 @@ do_backup_instance(void)
 
 	/* notify start of backup to PostgreSQL server */
 	time2iso(label, lengthof(label), current.start_time);
-	strncat(label, " with pg_probackup", lengthof(label));
+	strncat(label, " with pg_probackup", lengthof(label) -
+			strlen(" with pg_probackup"));
 	pg_start_backup(label, smooth_checkpoint, &current);
 
 	pgBackupGetPath(&current, database_path, lengthof(database_path),
diff --git a/src/parsexlog.c b/src/parsexlog.c
index be856bff..a0079b42 100644
--- a/src/parsexlog.c
+++ b/src/parsexlog.c
@@ -333,7 +333,7 @@ validate_wal(pgBackup *backup,
 	 */
 	if (backup->stream)
 	{
-		sprintf(backup_xlog_path, "/%s/%s/%s/%s",
+		snprintf(backup_xlog_path, sizeof(backup_xlog_path), "/%s/%s/%s/%s",
 				backup_instance_path, backup_id, DATABASE_DIR, PG_XLOG_DIR);
 
 		validate_backup_wal_from_start_to_stop(backup, backup_xlog_path, tli);