diff --git a/src/modules/mavlink/mavlink_main.cpp b/src/modules/mavlink/mavlink_main.cpp
index 6c97bfca71..28dd97fca1 100644
--- a/src/modules/mavlink/mavlink_main.cpp
+++ b/src/modules/mavlink/mavlink_main.cpp
@@ -149,10 +149,7 @@ mavlink_send_uart_bytes(mavlink_channel_t channel, const uint8_t *ch, int length
 		instance = Mavlink::get_instance(6);
 		break;
 #endif
-	}
-
-	/* no valid instance, bail */
-	if (!instance) {
+		default:
 		return;
 	}
 
@@ -211,9 +208,9 @@ mavlink_send_uart_bytes(mavlink_channel_t channel, const uint8_t *ch, int length
 static void usage(void);
 
 Mavlink::Mavlink() :
-	next(nullptr),
 	_device_name(DEFAULT_DEVICE_NAME),
 	_task_should_exit(false),
+	next(nullptr),
 	_mavlink_fd(-1),
 	_task_running(false),
 	_hil_enabled(false),
@@ -234,7 +231,6 @@ Mavlink::Mavlink() :
 	_subscribe_to_stream_rate(0.0f),
 	_flow_control_enabled(true),
 	_message_buffer({}),
-
 /* performance counters */
 	_loop_perf(perf_alloc(PC_ELAPSED, "mavlink"))
 {
@@ -2030,14 +2026,14 @@ Mavlink::task_main(int argc, char *argv[])
 		if (_subscribe_to_stream != nullptr) {
 			if (OK == configure_stream(_subscribe_to_stream, _subscribe_to_stream_rate)) {
 				if (_subscribe_to_stream_rate > 0.0f) {
-					warnx("stream %s on device %s enabled with rate %.1f Hz", _subscribe_to_stream, _device_name, _subscribe_to_stream_rate);
+					warnx("stream %s on device %s enabled with rate %.1f Hz", _subscribe_to_stream, _device_name, (double)_subscribe_to_stream_rate);
 
 				} else {
 					warnx("stream %s on device %s disabled", _subscribe_to_stream, _device_name);
 				}
 
 			} else {
-				warnx("stream %s not found", _subscribe_to_stream, _device_name);
+				warnx("stream %s on device %s not found", _subscribe_to_stream, _device_name);
 			}
 
 			delete _subscribe_to_stream;
@@ -2243,7 +2239,6 @@ Mavlink::stream(int argc, char *argv[])
 	const char *device_name = DEFAULT_DEVICE_NAME;
 	float rate = -1.0f;
 	const char *stream_name = nullptr;
-	int ch;
 
 	argc -= 2;
 	argv += 2;
@@ -2280,7 +2275,7 @@ Mavlink::stream(int argc, char *argv[])
 		i++;
 	}
 
-	if (!err_flag && rate >= 0.0 && stream_name != nullptr) {
+	if (!err_flag && rate >= 0.0f && stream_name != nullptr) {
 		Mavlink *inst = get_instance_for_device(device_name);
 
 		if (inst != nullptr) {
diff --git a/src/modules/mavlink/mavlink_main.h b/src/modules/mavlink/mavlink_main.h
index c7a7d32f84..25c0da8206 100644
--- a/src/modules/mavlink/mavlink_main.h
+++ b/src/modules/mavlink/mavlink_main.h
@@ -221,8 +221,6 @@ private:
 	int		_mavlink_fd;
 	bool		_task_running;
 
-	perf_counter_t	_loop_perf;			/**< loop performance counter */
-
 	/* states */
 	bool		_hil_enabled;		/**< Hardware In the Loop mode */
 	bool		_use_hil_gps;		/**< Accept GPS HIL messages (for example from an external motion capturing system to fake indoor gps) */
@@ -282,7 +280,7 @@ private:
 
 	pthread_mutex_t _message_buffer_mutex;
 
-
+	perf_counter_t	_loop_perf;			/**< loop performance counter */
 
 	/**
 	 * Send one parameter.
diff --git a/src/modules/mavlink/mavlink_orb_subscription.cpp b/src/modules/mavlink/mavlink_orb_subscription.cpp
index d432edd2b4..21d5219d34 100644
--- a/src/modules/mavlink/mavlink_orb_subscription.cpp
+++ b/src/modules/mavlink/mavlink_orb_subscription.cpp
@@ -63,7 +63,7 @@ MavlinkOrbSubscription::~MavlinkOrbSubscription()
 	free(_data);
 }
 
-const orb_id_t
+orb_id_t
 MavlinkOrbSubscription::get_topic()
 {
 	return _topic;
diff --git a/src/modules/mavlink/mavlink_orb_subscription.h b/src/modules/mavlink/mavlink_orb_subscription.h
index 5c6543e813..8c09772c8e 100644
--- a/src/modules/mavlink/mavlink_orb_subscription.h
+++ b/src/modules/mavlink/mavlink_orb_subscription.h
@@ -63,7 +63,7 @@ public:
 	 */
 	bool is_published();
 	void *get_data();
-	const orb_id_t get_topic();
+	orb_id_t get_topic();
 
 private:
 	const orb_id_t _topic;		/*< topic metadata */
diff --git a/src/modules/mavlink/mavlink_receiver.cpp b/src/modules/mavlink/mavlink_receiver.cpp
index 72b9ee83a3..53769e0cfe 100644
--- a/src/modules/mavlink/mavlink_receiver.cpp
+++ b/src/modules/mavlink/mavlink_receiver.cpp
@@ -932,6 +932,8 @@ void *MavlinkReceiver::start_helper(void *context)
 	rcv->receive_thread(NULL);
 
 	delete rcv;
+
+	return nullptr;
 }
 
 pthread_t
diff --git a/src/modules/mavlink/mavlink_stream.cpp b/src/modules/mavlink/mavlink_stream.cpp
index bb19d7e336..5ec30bd330 100644
--- a/src/modules/mavlink/mavlink_stream.cpp
+++ b/src/modules/mavlink/mavlink_stream.cpp
@@ -81,5 +81,9 @@ MavlinkStream::update(const hrt_abstime t)
 		/* interval expired, send message */
 		send(t);
 		_last_sent = (t / _interval) * _interval;
+
+		return 0;
 	}
+
+	return -1;
 }
diff --git a/src/modules/mavlink/mavlink_stream.h b/src/modules/mavlink/mavlink_stream.h
index def40d9adc..2979d20dee 100644
--- a/src/modules/mavlink/mavlink_stream.h
+++ b/src/modules/mavlink/mavlink_stream.h
@@ -63,9 +63,13 @@ public:
 	MavlinkStream *next;
 
 	MavlinkStream();
-	~MavlinkStream();
+	virtual ~MavlinkStream();
 	void set_interval(const unsigned int interval);
 	void set_channel(mavlink_channel_t channel);
+
+	/**
+	 * @return 0 if updated / sent, -1 if unchanged
+	 */
 	int update(const hrt_abstime t);
 	virtual MavlinkStream *new_instance() = 0;
 	virtual void subscribe(Mavlink *mavlink) = 0;