diff --git a/Sema/SemaDecl.cpp b/Sema/SemaDecl.cpp
index 9c8ec7f..ee3cc7a 100644
--- a/Sema/SemaDecl.cpp
+++ b/Sema/SemaDecl.cpp
@@ -154,7 +154,7 @@
   IdentifierInfo *VaIdent = &Context.Idents.get("__builtin_va_list");
   ScopedDecl *VaDecl = LookupScopedDecl(VaIdent, Decl::IDNS_Ordinary, 
                                           SourceLocation(), TUScope);
-  TypedefDecl *VaTypedef = dyn_cast_or_null<TypedefDecl>(VaDecl);
+  TypedefDecl *VaTypedef = cast<TypedefDecl>(VaDecl);
   Context.setBuiltinVaListType(Context.getTypedefType(VaTypedef));
 }
 
diff --git a/Sema/SemaExpr.cpp b/Sema/SemaExpr.cpp
index 28c6856..281e524 100644
--- a/Sema/SemaExpr.cpp
+++ b/Sema/SemaExpr.cpp
@@ -1906,7 +1906,8 @@
     ScopedDecl *IFace = LookupScopedDecl(NSIdent, Decl::IDNS_Ordinary, 
                                          SourceLocation(), TUScope);
     ObjcInterfaceDecl *strIFace = dyn_cast_or_null<ObjcInterfaceDecl>(IFace);
-    assert(strIFace && "missing '@interface NSConstantString'");
+    assert(strIFace && "missing @interface for NSConstantString"
+           "FIXME: need to predefine without breaking explicit inclusion");
     Context.setObjcConstantStringInterface(strIFace);
   }
   QualType t = Context.getObjcConstantStringInterface();