diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a73cd6b9de..efd0347bc9 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -9346,6 +9346,7 @@ do_pg_start_backup(const char *backupidstr, bool fast, char **labelfile)
 								BACKUP_LABEL_FILE)));
 			if (fwrite(labelfbuf.data, labelfbuf.len, 1, fp) != 1 ||
 				fflush(fp) != 0 ||
+				pg_fsync(fileno(fp)) != 0 ||
 				ferror(fp) ||
 				FreeFile(fp))
 				ereport(ERROR,