diff --git a/src/ngscopeclient/HistoryManager.cpp b/src/ngscopeclient/HistoryManager.cpp
index 6c35f667..23add750 100644
--- a/src/ngscopeclient/HistoryManager.cpp
+++ b/src/ngscopeclient/HistoryManager.cpp
@@ -219,7 +219,7 @@ void HistoryManager::LoadEmptyHistoryToSession(Session& session)
 
 	@param scopes		The instruments to add
 	@param deleteOld	True to delete old data that rolled off the end of the history buffer
-						Set false when loading waveforms from a sessio
+						Set false when loading waveforms from a session
 	@param pin			True to pin into history
 	@param nick			Nickname
  */
diff --git a/src/ngscopeclient/Session.cpp b/src/ngscopeclient/Session.cpp
index 2e4d74fb..9510ea82 100644
--- a/src/ngscopeclient/Session.cpp
+++ b/src/ngscopeclient/Session.cpp
@@ -112,25 +112,23 @@ void Session::ClearBackgroundThreads()
 {
 	LogTrace("Clearing background threads\n");
 
-	//Signal our threads to exit
-	//The sooner we do this, the faster they'll exit.
-	m_shuttingDown = true;
-
 	//Stop the trigger so there's no pending waveforms
-	StopTrigger();
+	StopTrigger(true);
+
+	//Shut down instrument threads.
+	//This has to happen before we terminate the WaveformThread, to avoid waveforms getting stuck
+	//which have been acquired but not processed
+	for(auto it : m_instrumentStates)
+		it.second->Close();
 
 	//Clear our trigger state
 	//Important to signal the WaveformProcessingThread so it doesn't block waiting on response that's not going to come
-	m_triggerArmed = false;
 	g_waveformReadyEvent.Clear();
 	g_rerenderDoneEvent.Clear();
 	g_waveformProcessedEvent.Signal();
 
-	//Shut down instrument threads
-	for(auto it : m_instrumentStates)
-		it.second->Close();
-
-	//Block until our processing threads exit
+	//Signal our other worker threads to exit, then wait until they do so
+	m_shuttingDown = true;
 	if(m_waveformThread)
 		m_waveformThread->join();
 	m_waveformThread = nullptr;
@@ -178,13 +176,10 @@ void Session::Clear()
 	//Might be redundant.
 	lock_guard<mutex> lock2(m_scopeMutex);
 
-	//Clear history before destroying scopes.
-	//This ordering is important since waveforms removed from history get pushed into the WaveformPool of the scopes,
-	//so the scopes must not have been destroyed yet.
-	m_history.clear();
-
 	//Delete scopes once we've terminated the threads
 	//Detach waveforms before we destroy the scope, since history owns them
+	//(but make sure they're actually *in* history first!)
+	m_history.AddHistory(m_oscilloscopes);
 	for(auto scope : m_oscilloscopes)
 	{
 		for(size_t i=0; i<scope->GetChannelCount(); i++)
@@ -197,6 +192,11 @@ void Session::Clear()
 		}
 	}
 
+	//Clear history before destroying scopes (but after detaching waveforms)
+	//This ordering is important since waveforms removed from history get pushed into the WaveformPool of the scopes,
+	//so the scopes must not have been destroyed yet.
+	m_history.clear();
+
 	m_oscilloscopes.clear();
 	m_psus.clear();
 	m_loads.clear();