diff --git a/plugins/pay.c b/plugins/pay.c
index 30b614d8d..f39ec20ac 100644
--- a/plugins/pay.c
+++ b/plugins/pay.c
@@ -876,6 +876,7 @@ static struct command_result *handle_pay(struct command *cmd,
 
 	/* Get capacities of local channels. */
 	return send_outreq(cmd, "listpeers", listpeers_done, forward_error, pc,
+			   /* gcc doesn't like zero-length format strings! */
 			   " ");
 }