diff --git a/repmgr-action-standby.c b/repmgr-action-standby.c
index 2272c6d0..1f3e42e8 100644
--- a/repmgr-action-standby.c
+++ b/repmgr-action-standby.c
@@ -770,7 +770,7 @@ do_standby_clone(void)
 			exit(ERR_BAD_CONFIG);
 		}
 
-		appendPQExpBufferStr(&command, " ");
+		appendPQExpBufferChar(&command, ' ');
 
 		/* Somewhat inconsistent, but pg_verifybackup doesn't accept a -D option  */
 		appendShellString(&command,