diff --git a/src/comm/MAVLinkProtocol.cc b/src/comm/MAVLinkProtocol.cc
index 1a01ed72772c0a722e97e358f393c55457dcf6b5..a8d5184f7b5e0772832214c83cf2092d9d424a93 100644
--- a/src/comm/MAVLinkProtocol.cc
+++ b/src/comm/MAVLinkProtocol.cc
@@ -109,7 +109,7 @@ void MAVLinkProtocol::receiveBytes(LinkInterface* link, QByteArray b)
             // Log data
             if (m_loggingEnabled)
             {
-                int len = MAVLINK_MAX_PACKET_LEN+sizeof(quint64);
+                const int len = MAVLINK_MAX_PACKET_LEN+sizeof(quint64);
                 uint8_t buf[len];
                 quint64 time = QGC::groundTimeUsecs();
                 memcpy(buf, (void*)&time, sizeof(quint64));