diff --git a/SAM.h b/SAM.h
index e82e8b7d..07142c8c 100644
--- a/SAM.h
+++ b/SAM.h
@@ -41,7 +41,7 @@ namespace client
 	const char SAM_DEST_REPLY_I2P_ERROR[] = "DEST REPLY RESULT=I2P_ERROR\n";
 	const char SAM_NAMING_LOOKUP[] = "NAMING LOOKUP";
 	const char SAM_NAMING_REPLY[] = "NAMING REPLY RESULT=OK NAME=ME VALUE=%s\n";
-	const char SAM_DATAGRAM_RECEIVED[] = "DATAGRAM RECEIVED DESTINATION=%s SIZE=%zu\n";
+	const char SAM_DATAGRAM_RECEIVED[] = "DATAGRAM RECEIVED DESTINATION=%s SIZE=%lu\n";
 	const char SAM_NAMING_REPLY_INVALID_KEY[] = "NAMING REPLY RESULT=INVALID_KEY NAME=%s\n";
 	const char SAM_NAMING_REPLY_KEY_NOT_FOUND[] = "NAMING REPLY RESULT=INVALID_KEY_NOT_FOUND NAME=%s\n";
 	const char SAM_PARAM_MIN[] = "MIN";