diff --git a/dlls/jscript/dispex.c b/dlls/jscript/dispex.c
index aa81de7ad75..1dd18fcc2ee 100644
--- a/dlls/jscript/dispex.c
+++ b/dlls/jscript/dispex.c
@@ -3282,8 +3282,14 @@ HRESULT jsdisp_define_property(jsdisp_t *obj, const WCHAR *name, property_desc_t
             if(desc->explicit_value) {
                 if(prop->type == PROP_JSVAL)
                     jsval_release(prop->u.val);
-                else
+                else {
+                    if(prop->type == PROP_EXTERN && obj->builtin_info->prop_delete) {
+                        hres = obj->builtin_info->prop_delete(obj, prop->u.id);
+                        if(FAILED(hres))
+                            return hres;
+                    }
                     prop->type = PROP_JSVAL;
+                }
                 hres = jsval_copy(desc->value, &prop->u.val);
                 if(FAILED(hres)) {
                     prop->u.val = jsval_undefined();
diff --git a/dlls/mshtml/tests/es5.js b/dlls/mshtml/tests/es5.js
index 3adb7cc1d61..efc3bf0f8d1 100644
--- a/dlls/mshtml/tests/es5.js
+++ b/dlls/mshtml/tests/es5.js
@@ -2153,6 +2153,23 @@ sync_test("builtin_context", function() {
     ok(obj.length === 1, "obj.length = " + obj.length);
 });
 
+sync_test("globals override", function() {
+    wineprop = 1337;  /* global */
+    ok(window.hasOwnProperty("wineprop"), "wineprop not a prop of window");
+    ok(window.wineprop === 1337, "window.wineprop = " + window.wineprop);
+    ok(wineprop === 1337, "wineprop = " + wineprop);
+
+    var r = Object.defineProperty(window, "wineprop", { value: 42, configurable: true });
+    ok(r === window, "defineProperty(window.wineprop) returned " + r);
+    ok(window.hasOwnProperty("wineprop"), "wineprop not a prop of window after override");
+    ok(window.wineprop === 42, "window.wineprop after override = " + window.wineprop);
+    ok(wineprop === 42, "wineprop after override = " + wineprop);
+
+    r = (delete window.wineprop);
+    ok(r === true, "delete window.wineprop returned " + r);
+    ok(!("wineprop" in window), "wineprop in window after delete");
+});
+
 sync_test("host this", function() {
     var tests = [ undefined, null, external.nullDisp, function() {}, [0], "foobar", true, 42, new Number(42), external.testHostContext(true), window, document ];
     var i, obj = Object.create(Function.prototype);