diff --git a/src/comm/MAVLinkProtocol.cc b/src/comm/MAVLinkProtocol.cc
index 12acc51a00ec352b775b499e91c5e983ed67b1c3..4c410f4e71620fe42423497b90c1d8116267853d 100644
--- a/src/comm/MAVLinkProtocol.cc
+++ b/src/comm/MAVLinkProtocol.cc
@@ -291,12 +291,11 @@ void MAVLinkProtocol::receiveBytes(LinkInterface* link, QByteArray b)
             // Log data
             if (m_loggingEnabled && m_logfile)
             {
-                const int len = MAVLINK_MAX_PACKET_LEN+sizeof(quint64);
-                uint8_t buf[len];
+                uint8_t buf[MAVLINK_MAX_PACKET_LEN+sizeof(quint64)];
                 quint64 time = QGC::groundTimeUsecs();
                 memcpy(buf, (void*)&time, sizeof(quint64));
                 // Write message to buffer
-                mavlink_msg_to_send_buffer(buf+sizeof(quint64), &message);
+                int len = mavlink_msg_to_send_buffer(buf+sizeof(quint64), &message);
                 QByteArray b((const char*)buf, len);
                 if(m_logfile->write(b) < static_cast<qint64>(MAVLINK_MAX_PACKET_LEN+sizeof(quint64)))
                 {