diff --git a/IDE/src/ui/SourceViewPanel.bf b/IDE/src/ui/SourceViewPanel.bf
index c6c88cdc..66266a98 100644
--- a/IDE/src/ui/SourceViewPanel.bf
+++ b/IDE/src/ui/SourceViewPanel.bf
@@ -1448,6 +1448,7 @@ namespace IDE.ui
 		public void DoRefreshCollapse(BfParser parser, int32 textVersion, IdSpan charIdSpan)
 		{
 			var bfCompiler = BfResolveCompiler;
+			var bfSystem = BfResolveSystem;
 
 			String explicitEmitTypeNames = scope .();
 			for (var explicitType in mExplicitEmitTypes)
@@ -1459,6 +1460,7 @@ namespace IDE.ui
 			var resolvePassData = parser.CreateResolvePassData(.None);
 			defer delete resolvePassData;
 
+			bfSystem.Lock(0);
 			var collapseData = bfCompiler.GetCollapseRegions(parser, resolvePassData, explicitEmitTypeNames, .. scope .());
 			using (mMonitor.Enter())
 			{
@@ -1468,6 +1470,7 @@ namespace IDE.ui
 				mQueuedCollapseData.mTextVersion = textVersion;
 				mQueuedCollapseData.mCharIdSpan = charIdSpan;
 			}
+			bfSystem.Unlock();
 		}
 
         public void DoFullClassify(ResolveParams resolveParams)
diff --git a/IDEHelper/Compiler/BfCompiler.cpp b/IDEHelper/Compiler/BfCompiler.cpp
index 8b7b33f2..add65531 100644
--- a/IDEHelper/Compiler/BfCompiler.cpp
+++ b/IDEHelper/Compiler/BfCompiler.cpp
@@ -9440,6 +9440,8 @@ BF_EXPORT bool BF_CALLTYPE BfCompiler_ClassifySource(BfCompiler* bfCompiler, BfP
 {
 	BP_ZONE("BfCompiler_ClassifySource");	
 	
+	bfCompiler->mSystem->AssertWeHaveLock();
+
 	String& autoCompleteResultString = *gTLStrReturn.Get();
 	autoCompleteResultString.clear();
 	
@@ -9464,6 +9466,8 @@ BF_EXPORT bool BF_CALLTYPE BfCompiler_ClassifySource(BfCompiler* bfCompiler, BfP
 
 BF_EXPORT const char* BF_CALLTYPE BfCompiler_GetCollapseRegions(BfCompiler* bfCompiler, BfParser* bfParser, BfResolvePassData* resolvePassData, char* explicitEmitTypeNames)
 {
+	bfCompiler->mSystem->AssertWeHaveLock();
+
 	String& outString = *gTLStrReturn.Get();
 	outString.Clear();
 	
@@ -10029,6 +10033,8 @@ BF_EXPORT const char* BF_CALLTYPE BfCompiler_GetCollapseRegions(BfCompiler* bfCo
 
 BF_EXPORT bool BF_CALLTYPE BfCompiler_VerifyTypeName(BfCompiler* bfCompiler, char* name, int cursorPos)
 {
+	bfCompiler->mSystem->AssertWeHaveLock();
+
 	String typeName = name;
 
 	auto system = bfCompiler->mSystem;
@@ -10096,7 +10102,7 @@ BF_EXPORT bool BF_CALLTYPE BfCompiler_VerifyTypeName(BfCompiler* bfCompiler, cha
 		resolvePassData.mAutoComplete->mModule = bfCompiler->mContext->mScratchModule;
 	}
 	resolvePassData.mParsers.Add(&parser);
-			
+				
 	SetAndRestoreValue<BfResolvePassData*> prevCompilerResolvePassData(bfCompiler->mResolvePassData, &resolvePassData);
 	SetAndRestoreValue<BfPassInstance*> prevPassInstance(bfCompiler->mPassInstance, &passInstance);
 
@@ -10248,6 +10254,8 @@ BF_EXPORT int BF_CALLTYPE BfCompiler_GetTypeId(BfCompiler* bfCompiler, const cha
 
 BF_EXPORT const char* BF_CALLTYPE BfCompiler_GetTypeInfo(BfCompiler* bfCompiler, const char* name)
 {
+	bfCompiler->mSystem->AssertWeHaveLock();
+
 	String& outString = *gTLStrReturn.Get();
 	outString = "";
 
@@ -10564,6 +10572,8 @@ BF_EXPORT void BF_CALLTYPE BfCompiler_FileChanged(BfCompiler* bfCompiler, const
 
 BF_EXPORT const char* BF_CALLTYPE BfCompiler_GetSymbolReferences(BfCompiler* bfCompiler, BfPassInstance* bfPassInstance, BfResolvePassData* resolvePassData)
 {
+	bfCompiler->mSystem->AssertWeHaveLock();
+
 	BP_ZONE("BfCompiler_GetSymbolReferences");
 
 	String& outString = *gTLStrReturn.Get();
diff --git a/IDEHelper/Compiler/BfSystem.cpp b/IDEHelper/Compiler/BfSystem.cpp
index 4fb59ae9..b5bb427f 100644
--- a/IDEHelper/Compiler/BfSystem.cpp
+++ b/IDEHelper/Compiler/BfSystem.cpp
@@ -3754,7 +3754,9 @@ void BfSystem::Unlock()
 
 void BfSystem::AssertWeHaveLock()
 {
-	//mSystemLock.mCritSect
+#ifdef BF_PLATFORM_WINDOWS	
+	BF_ASSERT_REL(((CRITICAL_SECTION*)mSystemLock.mCritSect)->OwningThread == (HANDLE)(uintptr)::GetCurrentThreadId());
+#endif
 }
 
 void BfSystem::RemoveDeletedParsers()