diff --git a/FDTD/engine.cpp b/FDTD/engine.cpp
index b93aaca..0d1e511 100644
--- a/FDTD/engine.cpp
+++ b/FDTD/engine.cpp
@@ -73,6 +73,13 @@ void Engine::InitExtensions()
 	}
 }
 
+void Engine::ClearExtensions()
+{
+	for (size_t n=0;n<m_Eng_exts.size();++n)
+		delete m_Eng_exts.at(n);
+	m_Eng_exts.clear();
+}
+
 void Engine::Reset()
 {
 	Delete_N_3DArray(volt,numLines);
@@ -83,9 +90,7 @@ void Engine::Reset()
 	file_et.close();
 	file_ht.close();
 
-	for (size_t n=0;n<m_Eng_exts.size();++n)
-		delete m_Eng_exts.at(n);
-	m_Eng_exts.clear();
+	ClearExtensions();
 }
 
 void Engine::UpdateVoltages(unsigned int startX, unsigned int numX)
diff --git a/FDTD/engine.h b/FDTD/engine.h
index 27d7493..dbad0b4 100644
--- a/FDTD/engine.h
+++ b/FDTD/engine.h
@@ -80,6 +80,7 @@ protected:
 	unsigned int numTS;
 
 	virtual void InitExtensions();
+	virtual void ClearExtensions();
 	vector<Engine_Extension*> m_Eng_exts;
 
 	ofstream file_et, file_ht; //excite signal dump file
diff --git a/FDTD/engine_multithread.cpp b/FDTD/engine_multithread.cpp
index b9c4c1d..55eed90 100644
--- a/FDTD/engine_multithread.cpp
+++ b/FDTD/engine_multithread.cpp
@@ -133,8 +133,9 @@ void Engine_Multithread::Init()
 
 void Engine_Multithread::Reset()
 {
-	if (!m_stopThreads) {
-		// prevent multiple invocations
+	if (!m_stopThreads) // prevent multiple invocations
+	{
+		ClearExtensions(); //prevent extensions from interfering with thread reset...
 
 		// stop the threads
 		//NS_Engine_Multithread::DBG().cout() << "stopping all threads" << endl;