diff --git a/include/gui/glscope.h b/include/gui/glscope.h
index 7a314449f..66b71e74e 100644
--- a/include/gui/glscope.h
+++ b/include/gui/glscope.h
@@ -103,6 +103,7 @@ private:
 	int m_sampleRates[16];
 	BitfieldIndex<m_memHistorySizeLog2> m_memTraceIndex;   //!< current index of trace being written
 	BitfieldIndex<m_memHistorySizeLog2> m_memTraceHistory; //!< trace index shift into history
+	int m_memTraceIndexMax;
 	bool m_memTraceRecall;
 	std::vector<Complex> m_mathTrace;
 	std::vector<Complex>* m_displayTrace;
diff --git a/sdrbase/gui/glscope.cpp b/sdrbase/gui/glscope.cpp
index fa643e546..12d4b47c4 100644
--- a/sdrbase/gui/glscope.cpp
+++ b/sdrbase/gui/glscope.cpp
@@ -23,6 +23,7 @@ GLScope::GLScope(QWidget* parent) :
 	m_orientation(Qt::Horizontal),
 	m_memTraceIndex(0),
 	m_memTraceHistory(0),
+	m_memTraceIndexMax(0),
 	m_memTraceRecall(false),
 	m_displayTrace(&m_rawTrace[0]),
 	m_oldTraceSize(-1),
@@ -197,6 +198,11 @@ void GLScope::newTrace(const std::vector<Complex>& trace, int sampleRate)
 		m_rawTrace[m_memTraceIndex] = trace;
 		m_sampleRates[m_memTraceIndex] = sampleRate;
 
+		if(m_memTraceIndexMax < (1<<m_memHistorySizeLog2))
+		{
+			m_memTraceIndexMax++;
+		}
+
 		//m_sampleRate = sampleRate; // sampleRate comes from scopeVis
 		m_dataChanged = true;
 
@@ -1929,9 +1935,12 @@ void GLScope::setTriggerPre(Real triggerPre)
 
 void GLScope::setMemHistoryShift(int value)
 {
-	m_memTraceHistory = value;
-	m_configChanged = true;
-	update();
+	if (value < m_memTraceIndexMax)
+	{
+		m_memTraceHistory = value;
+		m_configChanged = true;
+		update();
+	}
 }
 
 void GLScope::connectTimer(const QTimer& timer)