diff --git a/libtorrent/src/alert.cpp b/libtorrent/src/alert.cpp
index a08094c0..1d343994 100644
--- a/libtorrent/src/alert.cpp
+++ b/libtorrent/src/alert.cpp
@@ -354,7 +354,7 @@ namespace libtorrent {
 	std::string dht_reply_data_alert::message() const
 	{
 		char msg[200];
-		snprintf(msg, sizeof(msg), "reply to dht getData received %d entries", m_lst.size());
+		snprintf(msg, sizeof(msg), "reply to dht getData received %lu entries", m_lst.size());
 		return msg;
 	}