diff --git a/plugins/keysend.c b/plugins/keysend.c
index 186ae269b..5c6075f05 100644
--- a/plugins/keysend.c
+++ b/plugins/keysend.c
@@ -134,7 +134,7 @@ static struct command_result *htlc_accepted_call(struct command *cmd,
 
 	ki = tal(cmd, struct keysend_in);
 	memcpy(&ki->payment_preimage, preimage_field->value, 32);
-	ki->label = tal_fmt(ki, "keysend-%lu.%09lu", now.ts.tv_sec, now.ts.tv_nsec);
+	ki->label = tal_fmt(ki, "keysend-%lu.%09lu", (unsigned long)now.ts.tv_sec, now.ts.tv_nsec);
 	ki->payload = tal_steal(ki, payload);
 	ki->preimage_field = preimage_field;