diff --git a/IDEHelper/Compiler/BfContext.h b/IDEHelper/Compiler/BfContext.h
index 6efd1fdd..c9ab4227 100644
--- a/IDEHelper/Compiler/BfContext.h
+++ b/IDEHelper/Compiler/BfContext.h
@@ -143,10 +143,11 @@ public:
 
 	BfPopulateType mPopulateType;
 	BfTypeReference* mCurBaseTypeRef;
+	BfTypeInstance* mCurBaseType;
 	BfTypeReference* mCurAttributeTypeRef;
 	BfFieldDef* mCurFieldDef;	
 	BfTypeDef* mCurTypeDef;
-	BfTypeDef* mForceActiveTypeDef;
+	BfTypeDef* mForceActiveTypeDef;	
 	ResolveKind mResolveKind;
 	BfAstNode* mCurVarInitializer;
 	int mArrayInitializerSize;
@@ -160,6 +161,7 @@ public:
 
 		mPopulateType = BfPopulateType_Identity;
 		mCurBaseTypeRef = NULL;
+		mCurBaseType = NULL;
 		mCurFieldDef = NULL;
 		mCurAttributeTypeRef = NULL;
 		mCurTypeDef = NULL;
diff --git a/IDEHelper/Compiler/BfModuleTypeUtils.cpp b/IDEHelper/Compiler/BfModuleTypeUtils.cpp
index 44a593d5..9f2df9a8 100644
--- a/IDEHelper/Compiler/BfModuleTypeUtils.cpp
+++ b/IDEHelper/Compiler/BfModuleTypeUtils.cpp
@@ -3022,7 +3022,10 @@ void BfModule::DoPopulateType(BfType* resolvedTypeRef, BfPopulateType populateTy
 			bool populateBase = !typeInstance->mTypeFailed;			
 			auto checkType = ResolveTypeRef(checkTypeRef, BfPopulateType_Declaration);
 			if ((checkType != NULL) && (!checkType->IsInterface()) && (populateBase))
+			{
+				SetAndRestoreValue<BfTypeInstance*> prevBaseType(mContext->mCurTypeState->mCurBaseType, checkType->ToTypeInstance());
 				PopulateType(checkType, BfPopulateType_Data);
+			}
 
 			if (typeInstance->mDefineState >= BfTypeDefineState_Defined)
 			{
@@ -12793,6 +12796,19 @@ bool BfModule::TypeIsSubTypeOf(BfTypeInstance* srcType, BfTypeInstance* wantType
 
 	if (srcType->mDefineState < BfTypeDefineState_HasInterfaces)
 	{
+		if (srcType->mDefineState == BfTypeDefineState_ResolvingBaseType)
+		{
+			auto typeState = mContext->mCurTypeState;
+			while (typeState != NULL)
+			{
+				if ((typeState->mTypeInstance == srcType) && (typeState->mCurBaseType != NULL))
+				{
+					return TypeIsSubTypeOf(typeState->mCurBaseType, wantType, checkAccessibility);
+				}
+				typeState = typeState->mPrevState;
+			}
+		}
+
 		// Type is incomplete.  We don't do the IsIncomplete check here because of re-entry
 		//  While handling 'var' resolution, we don't want to force a PopulateType reentry 
 		//  but we do have enough information for TypeIsSubTypeOf
diff --git a/IDEHelper/Tests/src/Classes.bf b/IDEHelper/Tests/src/Classes.bf
new file mode 100644
index 00000000..b4d4c0f0
--- /dev/null
+++ b/IDEHelper/Tests/src/Classes.bf
@@ -0,0 +1,26 @@
+namespace Tests
+{
+	class Classes
+	{
+		public abstract class Plugin<T> where T : Plugin<T>, new, class
+		{
+			public abstract void OnLoad();
+			public abstract void OnUnload();
+		}
+
+		public abstract class ProgramPlugin<T> : Plugin<T> where T : ProgramPlugin<T>
+		{
+		}
+
+		public class ExamplePlugin : ProgramPlugin<ExamplePlugin>
+		{
+			public override void OnLoad()
+			{
+			}
+
+			public override void OnUnload()
+			{
+			}
+		}
+	}
+}