diff --git a/dlls/mshtml/htmlscript.h b/dlls/mshtml/htmlscript.h
index 6d608d525a1..30b46677395 100644
--- a/dlls/mshtml/htmlscript.h
+++ b/dlls/mshtml/htmlscript.h
@@ -48,6 +48,7 @@ IDispatch *script_parse_event(HTMLInnerWindow*,LPCWSTR);
 HRESULT exec_script(HTMLInnerWindow*,const WCHAR*,const WCHAR*,VARIANT*);
 void update_browser_script_mode(GeckoBrowser*,IUri*);
 BOOL find_global_prop(HTMLInnerWindow*,const WCHAR*,DWORD,ScriptHost**,DISPID*);
+HRESULT global_prop_still_exists(HTMLInnerWindow*,global_prop_t*);
 IDispatch *get_script_disp(ScriptHost*);
 IActiveScriptSite *get_first_script_site(HTMLInnerWindow*);
 void initialize_script_global(HTMLInnerWindow*);
diff --git a/dlls/mshtml/htmlwindow.c b/dlls/mshtml/htmlwindow.c
index 1343c75ba34..d9ecf9d3d29 100644
--- a/dlls/mshtml/htmlwindow.c
+++ b/dlls/mshtml/htmlwindow.c
@@ -3324,8 +3324,10 @@ HRESULT search_window_props(HTMLInnerWindow *This, const WCHAR *name, DWORD grfd
     for(i=0; i < This->global_prop_cnt; i++) {
         /* FIXME: case sensitivity */
         if(!wcscmp(This->global_props[i].name, name)) {
-            *pid = MSHTML_DISPID_CUSTOM_MIN+i;
-            return S_OK;
+            HRESULT hres = global_prop_still_exists(This, &This->global_props[i]);
+            if(hres == S_OK)
+                *pid = MSHTML_DISPID_CUSTOM_MIN + i;
+            return (hres == DISP_E_MEMBERNOTFOUND) ? DISP_E_UNKNOWNNAME : hres;
         }
     }
 
diff --git a/dlls/mshtml/script.c b/dlls/mshtml/script.c
index 7ac26e63a3b..73bb8e1d5c6 100644
--- a/dlls/mshtml/script.c
+++ b/dlls/mshtml/script.c
@@ -85,6 +85,7 @@ struct ScriptHost {
     SCRIPTSTATE script_state;
 
     HTMLInnerWindow *window;
+    IDispatchEx *script_dispex;
 
     GUID guid;
     struct list entry;
@@ -255,6 +256,18 @@ static BOOL init_script_engine(ScriptHost *script_host, IActiveScript *script)
             if(is_second_init)
                 set_script_prop(first_host->script, SCRIPTPROP_ABBREVIATE_GLOBALNAME_RESOLUTION, &var);
         }
+
+        if(IsEqualGUID(&script_host->guid, &CLSID_JScript)) {
+            IDispatch *script_disp;
+
+            hres = IActiveScript_GetScriptDispatch(script, NULL, &script_disp);
+            if(FAILED(hres))
+                WARN("GetScriptDispatch failed: %08lx\n", hres);
+            else {
+                IDispatch_QueryInterface(script_disp, &IID_IDispatchEx, (void**)&script_host->script_dispex);
+                IDispatch_Release(script_disp);
+            }
+        }
     }else {
        WARN("AddNamedItem failed: %08lx\n", hres);
     }
@@ -288,6 +301,8 @@ static void release_script_engine(ScriptHost *This)
         unlink_ref(&This->parse);
     }
 
+    if(This->script_dispex)
+        IDispatchEx_Release(This->script_dispex);
     IActiveScript_Release(This->script);
     This->script = NULL;
     This->script_state = SCRIPTSTATE_UNINITIALIZED;
@@ -1825,6 +1840,48 @@ BOOL find_global_prop(HTMLInnerWindow *window, const WCHAR *name, DWORD flags, S
     return FALSE;
 }
 
+HRESULT global_prop_still_exists(HTMLInnerWindow *window, global_prop_t *prop)
+{
+    HRESULT hres;
+
+    switch(prop->type) {
+    case GLOBAL_SCRIPTVAR: {
+        DWORD properties;
+
+        if(!prop->script_host->script)
+            return E_UNEXPECTED;
+        if(!prop->script_host->script_dispex)
+            return S_OK;
+        return IDispatchEx_GetMemberProperties(prop->script_host->script_dispex, prop->id, 0, &properties);
+    }
+    case GLOBAL_ELEMENTVAR: {
+        IHTMLElement *elem;
+
+        hres = IHTMLDocument3_getElementById(&window->doc->IHTMLDocument3_iface, prop->name, &elem);
+        if(FAILED(hres))
+            return hres;
+
+        if(!elem)
+            return DISP_E_MEMBERNOTFOUND;
+        IHTMLElement_Release(elem);
+        return S_OK;
+    }
+    case GLOBAL_FRAMEVAR: {
+        HTMLOuterWindow *frame;
+
+        hres = get_frame_by_name(window->base.outer_window, prop->name, FALSE, &frame);
+        if(FAILED(hres))
+            return hres;
+
+        return frame ? S_OK : DISP_E_MEMBERNOTFOUND;
+    }
+    default:
+        break;
+    }
+
+    return S_OK;
+}
+
 static BOOL is_jscript_available(void)
 {
     static BOOL available, checked;
diff --git a/dlls/mshtml/tests/documentmode.js b/dlls/mshtml/tests/documentmode.js
index 53372ac7752..ca89fdadbdb 100644
--- a/dlls/mshtml/tests/documentmode.js
+++ b/dlls/mshtml/tests/documentmode.js
@@ -1449,8 +1449,89 @@ sync_test("delete_prop", function() {
     ok(obj.globalprop4, "globalprop4 = " + globalprop4);
     r = (delete globalprop4);
     ok(r, "delete returned " + r);
-    todo_wine.
     ok(!("globalprop4" in obj), "globalprop4 is still in obj");
+
+    globalprop5 = true;
+    ok(obj.globalprop5, "globalprop5 = " + globalprop5);
+    try {
+        r = (delete window.globalprop5);
+        ok(v >= 9, "did not get an expected exception deleting globalprop5");
+        ok(r, "delete returned " + r);
+        todo_wine.
+        ok(!("globalprop5" in obj), "globalprop5 is still in obj");
+    }catch(ex) {
+        ok(v < 9, "expected exception deleting globalprop5");
+        ok(ex.number === 0xa01bd - 0x80000000, "deleting globalprop5 threw " + ex.number);
+        ok("globalprop5" in obj, "globalprop5 is not in obj");
+    }
+
+    document.body.innerHTML = '<div id="winetest"/>';
+    ok("winetest" in obj, "winetest not in obj");
+    try {
+        r = (delete window.winetest);
+        ok(v >= 9, "did not get an expected exception deleting winetest");
+        ok(r, "delete returned " + r);
+    }catch(ex) {
+        ok(v < 9, "expected exception deleting winetest");
+        ok(ex.number === 0xa01bd - 0x80000000, "deleting winetest threw " + ex.number);
+    }
+    ok("winetest" in obj, "winetest is not in obj");
+    document.body.innerHTML = "";
+    ok(!("winetest" in obj), "winetest is still in obj");
+
+    document.body.innerHTML = '<div id="foobar"/>';
+    ok("foobar" in obj, "foobar not in obj");
+    window.foobar = "1234";
+    ok(obj.foobar === "1234", "foobar = " + obj.foobar);
+    document.body.innerHTML = "";
+    ok("foobar" in obj, "foobar is not in obj");
+    ok(obj.foobar === "1234", "foobar = " + obj.foobar);
+    try {
+        r = (delete window.foobar);
+        ok(v >= 9, "did not get an expected exception deleting foobar");
+        ok(r, "delete returned " + r);
+        ok(!("foobar" in obj), "foobar is still in obj");
+    }catch(ex) {
+        ok(v < 9, "expected exception deleting foobar");
+        ok(ex.number === 0xa01bd - 0x80000000, "deleting foobar threw " + ex.number);
+        ok("foobar" in obj, "foobar is not in obj");
+    }
+
+    document.body.innerHTML = '<div id="barfoo"/>';
+    ok("barfoo" in obj, "barfoo not in obj");
+    window.barfoo = "5678";
+    ok(obj.barfoo === "5678", "barfoo = " + obj.barfoo);
+    try {
+        r = (delete window.barfoo);
+        ok(v >= 9, "did not get an expected exception deleting barfoo");
+        ok(r, "delete returned " + r);
+        ok(obj.barfoo !== "5678", "barfoo is still 5678");
+    }catch(ex) {
+        ok(v < 9, "expected exception deleting barfoo");
+        ok(ex.number === 0xa01bd - 0x80000000, "deleting barfoo threw " + ex.number);
+        ok(obj.barfoo === "5678", "barfoo = " + obj.barfoo);
+    }
+    ok("barfoo" in obj, "barfoo is not in obj");
+    document.body.innerHTML = "";
+    if(v < 9)
+        ok("barfoo" in obj, "barfoo is not in obj");
+    else
+        ok(!("barfoo" in obj), "barfoo is still in obj");
+
+    document.body.innerHTML = '<iframe id="testwine"/>';
+    ok("testwine" in obj, "testwine not in obj");
+    try {
+        r = (delete window.testwine);
+        ok(v >= 9, "did not get an expected exception deleting testwine");
+        ok(r, "delete returned " + r);
+    }catch(ex) {
+        ok(v < 9, "expected exception deleting testwine");
+        ok(ex.number === 0xa01bd - 0x80000000, "deleting testwine threw " + ex.number);
+    }
+    ok("testwine" in obj, "testwine is not in obj");
+
+    document.body.innerHTML = "";
+    ok(!("testwine" in obj), "testwine is still in obj");
 });
 
 sync_test("detached arguments", function() {