diff --git a/include/EnvelopeAndLfoParameters.h b/include/EnvelopeAndLfoParameters.h
index 4bafbde4b..747bb94c2 100644
--- a/include/EnvelopeAndLfoParameters.h
+++ b/include/EnvelopeAndLfoParameters.h
@@ -121,6 +121,7 @@ private:
 	static LfoInstances * s_lfoInstances;
 	bool m_used;
 
+	QMutex m_paramMutex;
 
 	FloatModel m_predelayModel;
 	FloatModel m_attackModel;
diff --git a/src/core/EnvelopeAndLfoParameters.cpp b/src/core/EnvelopeAndLfoParameters.cpp
index d044f98f3..d1fbaeb03 100644
--- a/src/core/EnvelopeAndLfoParameters.cpp
+++ b/src/core/EnvelopeAndLfoParameters.cpp
@@ -291,6 +291,8 @@ void EnvelopeAndLfoParameters::fillLevel( float * _buf, f_cnt_t _frame,
 						const f_cnt_t _release_begin,
 						const fpp_t _frames )
 {
+	QMutexLocker m(&m_paramMutex);
+
 	if( _frame < 0 || _release_begin < 0 )
 	{
 		return;
@@ -402,6 +404,8 @@ void EnvelopeAndLfoParameters::loadSettings( const QDomElement & _this )
 
 void EnvelopeAndLfoParameters::updateSampleVars()
 {
+	QMutexLocker m(&m_paramMutex);
+
 	const float frames_per_env_seg = SECS_PER_ENV_SEGMENT *
 				Engine::mixer()->processingSampleRate();
 	// TODO: Remove the expKnobVals, time should be linear