diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index e058a45..9c4ccc9 100644
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -451,7 +451,8 @@
 
 /// GetVTTParameter - Return the VTT parameter that should be passed to a
 /// base constructor/destructor with virtual bases.
-static llvm::Value *GetVTTParameter(CodeGenFunction &CGF, GlobalDecl GD) {
+static llvm::Value *GetVTTParameter(CodeGenFunction &CGF, GlobalDecl GD,
+                                    bool ForVirtualBase) {
   if (!CodeGenVTables::needsVTTParameter(GD)) {
     // This constructor/destructor does not need a VTT parameter.
     return 0;
@@ -469,6 +470,7 @@
   if (RD == Base) {
     assert(!CodeGenVTables::needsVTTParameter(CGF.CurGD) &&
            "doing no-op VTT offset in base dtor/ctor?");
+    assert(!ForVirtualBase && "Can't have same class as virtual base!");
     SubVTTIndex = 0;
   } else {
     SubVTTIndex = CGF.CGM.getVTables().getSubVTTIndex(RD, Base);
@@ -1249,7 +1251,7 @@
     return;
   }
 
-  llvm::Value *VTT = GetVTTParameter(*this, GlobalDecl(D, Type));
+  llvm::Value *VTT = GetVTTParameter(*this, GlobalDecl(D, Type), ForVirtualBase);
   llvm::Value *Callee = CGM.GetAddrOfCXXConstructor(D, Type);
 
   EmitCXXMemberCall(D, Callee, ReturnValueSlot(), This, VTT, ArgBeg, ArgEnd);
@@ -1270,7 +1272,8 @@
   ++I;
 
   // vtt
-  if (llvm::Value *VTT = GetVTTParameter(*this, GlobalDecl(Ctor, CtorType))) {
+  if (llvm::Value *VTT = GetVTTParameter(*this, GlobalDecl(Ctor, CtorType),
+                                         /*ForVirtualBase=*/false)) {
     QualType VoidPP = getContext().getPointerType(getContext().VoidPtrTy);
     DelegateArgs.push_back(std::make_pair(RValue::get(VTT), VoidPP));
 
@@ -1324,7 +1327,8 @@
                                             CXXDtorType Type,
                                             bool ForVirtualBase,
                                             llvm::Value *This) {
-  llvm::Value *VTT = GetVTTParameter(*this, GlobalDecl(DD, Type));
+  llvm::Value *VTT = GetVTTParameter(*this, GlobalDecl(DD, Type), 
+                                     ForVirtualBase);
   llvm::Value *Callee = CGM.GetAddrOfCXXDestructor(DD, Type);
   
   EmitCXXMemberCall(DD, Callee, ReturnValueSlot(), This, VTT, 0, 0);