diff -r 3949b825f4bf -r faf0414a8b51 libpurple/protocols/msn/p2p.c
--- a/libpurple/protocols/msn/p2p.c	Tue Aug 20 14:04:56 2013 +0200
+++ b/libpurple/protocols/msn/p2p.c	Wed Aug 21 14:59:29 2013 +0200
@@ -133,7 +133,9 @@
 			header->opcode = msn_pop8(wire);
 			header->message_len = msn_pop16be(wire);
 			header->base_id = msn_pop32be(wire);
-			if (header->header_len + header->message_len + P2P_PACKET_FOOTER_SIZE > max_len) {
+			if ((gsize)header->header_len + header->message_len +
+				P2P_PACKET_FOOTER_SIZE > max_len)
+			{
 				/* Invalid header and data length */
 				len = 0;
 				break;