diff --git a/include/dsp/threadedsamplesink.h b/include/dsp/threadedsamplesink.h
index f134b0e82..82999d3d8 100644
--- a/include/dsp/threadedsamplesink.h
+++ b/include/dsp/threadedsamplesink.h
@@ -63,7 +63,7 @@ public:
 	void start(); //!< this thread start()
 	void stop();  //!< this thread exit() and wait()
 
-	bool handleSinkMessage(Message& cmd); //!< Send message to sink synchronously
+	bool handleSinkMessage(const Message& cmd); //!< Send message to sink synchronously
 	void feed(SampleVector::const_iterator begin, SampleVector::const_iterator end, bool positiveOnly); //!< Feed sink with samples
 
 	QString getSampleSinkObjectName() const;
diff --git a/sdrbase/dsp/threadedsamplesink.cpp b/sdrbase/dsp/threadedsamplesink.cpp
index e18f485cd..1cce36092 100644
--- a/sdrbase/dsp/threadedsamplesink.cpp
+++ b/sdrbase/dsp/threadedsamplesink.cpp
@@ -110,7 +110,7 @@ void ThreadedSampleSink::feed(SampleVector::const_iterator begin, SampleVector::
 	m_threadedSampleFifo->writeToFifo(begin, end);
 }
 
-bool ThreadedSampleSink::handleSinkMessage(Message& cmd)
+bool ThreadedSampleSink::handleSinkMessage(const Message& cmd)
 {
 	return m_sampleSink->handleMessage(cmd);
 }