Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -5496,6 +5496,8 @@
   bool ZeroInitialization(const Expr *E) {
     auto Offset = Info.Ctx.getTargetNullPointerValue(E->getType());
     Result.set((Expr*)nullptr, 0, false, true, Offset);
+    Result.getLValueDesignator() =
+        SubobjectDesignator(E->getType()->getPointeeType());
     return true;
   }
 
Index: clang/test/SemaCXX/null-cast.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/null-cast.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct A {};
+struct B : virtual A {};
+
+void foo() {
+  (void)static_cast<A&>(*(B *)0); // expected-warning {{binding dereferenced null pointer to reference has undefined behavior}}
+}