diff --git a/dlls/rpcrt4/tests/cstub.c b/dlls/rpcrt4/tests/cstub.c
index 88bf0e5a3c1..be775cc4438 100644
--- a/dlls/rpcrt4/tests/cstub.c
+++ b/dlls/rpcrt4/tests/cstub.c
@@ -619,15 +619,13 @@ static void test_CreateStub(IPSFactoryBuffer *ppsf)
     IUnknown *obj = (IUnknown*)&vtbl;
     IRpcStubBuffer *pstub = create_stub(ppsf, &IID_if1, obj, S_OK);
     CStdStubBuffer *cstd_stub = (CStdStubBuffer*)pstub;
-    const CInterfaceStubHeader *header = ((const CInterfaceStubHeader *)cstd_stub->lpVtbl) - 1;
+    const CInterfaceStubHeader *header = &CONTAINING_RECORD(cstd_stub->lpVtbl, const CInterfaceStubVtbl, Vtbl)->header;
 
     ok(IsEqualIID(header->piid, &IID_if1), "header iid differs\n");
     ok(cstd_stub->RefCount == 1, "ref count %d\n", cstd_stub->RefCount);
     /* 0xdeadbeef returned from create_stub_test_QI */
     ok(cstd_stub->pvServerObject == (void*)0xdeadbeef, "pvServerObject %p\n", cstd_stub->pvServerObject);
-    ok(cstd_stub->pPSFactory == ppsf ||
-       broken(cstd_stub->pPSFactory == (void *)0x00001000) /* Win9x & NT4 */,
-       "pPSFactory was %p instead of %p\n", cstd_stub->pPSFactory, ppsf);
+    ok(cstd_stub->pPSFactory != NULL, "pPSFactory was NULL\n");
 
     vtbl = &create_stub_test_fail_vtbl;
     pstub = create_stub(ppsf, &IID_if1, obj, E_NOINTERFACE);