diff --git a/src/protocol_misc.c b/src/protocol_misc.c
index 625c006f..4528f3fc 100644
--- a/src/protocol_misc.c
+++ b/src/protocol_misc.c
@@ -100,7 +100,7 @@ bool send_ping(connection_t *c) {
 	c->status.pinged = true;
 	c->last_ping_time = now;
 
-	return send_request(c, "%d %zu %ld", PING, c->last_ping_time.tv_sec, c->last_ping_time.tv_usec);
+	return send_request(c, "%d %zu %ld", PING, (size_t)c->last_ping_time.tv_sec, c->last_ping_time.tv_usec);
 }
 
 bool ping_h(connection_t *c, const char *request) {