diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 330e058c5f..e213329075 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -8733,7 +8733,7 @@ do_pg_backup_start(const char *backupidstr, bool fast, List **tablespaces,
 				 errmsg("backup label too long (max %d bytes)",
 						MAXPGPATH)));
 
-	memcpy(state->name, backupidstr, strlen(backupidstr));
+	memcpy(state->name, backupidstr, strlen(backupidstr) + 1);
 
 	/*
 	 * Mark backup active in shared memory.  We must do full-page WAL writes