diff --git a/dlls/mshtml/dispex.c b/dlls/mshtml/dispex.c
index 9a2cebd70b9..791f361e0bf 100644
--- a/dlls/mshtml/dispex.c
+++ b/dlls/mshtml/dispex.c
@@ -343,6 +343,15 @@ static HRESULT process_interface(dispex_data_t *data, tid_t tid, ITypeInfo *disp
     return S_OK;
 }
 
+void dispex_info_add_interface(dispex_data_t *info, tid_t tid)
+{
+    HRESULT hres;
+
+    hres = process_interface(info, tid, NULL);
+    if(FAILED(hres))
+        ERR("process_interface failed: %08x\n", hres);
+}
+
 static int dispid_cmp(const void *p1, const void *p2)
 {
     return ((const func_info_t*)p1)->id - ((const func_info_t*)p2)->id;
@@ -386,15 +395,15 @@ static dispex_data_t *preprocess_dispex_data(const dispex_static_data_t *desc)
     }
     list_add_tail(&dispex_data_list, &data->entry);
 
+    if(desc->init_info)
+        desc->init_info(data);
+
     for(tid = desc->iface_tids; *tid; tid++) {
         hres = process_interface(data, *tid, dti);
         if(FAILED(hres))
             break;
     }
 
-    if(desc->additional_tid)
-        process_interface(data, desc->additional_tid, NULL);
-
     if(!data->func_cnt) {
         heap_free(data->funcs);
         data->name_table = NULL;
diff --git a/dlls/mshtml/htmlwindow.c b/dlls/mshtml/htmlwindow.c
index b75c9bad6ff..54cd0782994 100644
--- a/dlls/mshtml/htmlwindow.c
+++ b/dlls/mshtml/htmlwindow.c
@@ -2936,6 +2936,11 @@ static void HTMLWindow_bind_event(DispatchEx *dispex, int eid)
     dispex_get_vtbl(&This->doc->node.event_target.dispex)->bind_event(&This->doc->node.event_target.dispex, eid);
 }
 
+static void HTMLWindow_init_dispex_info(dispex_data_t *info)
+{
+    dispex_info_add_interface(info, IHTMLWindow5_tid);
+}
+
 static const dispex_static_data_vtbl_t HTMLWindow_dispex_vtbl = {
     NULL,
     NULL,
@@ -2957,7 +2962,7 @@ static dispex_static_data_t HTMLWindow_dispex = {
     &HTMLWindow_dispex_vtbl,
     DispHTMLWindow2_tid,
     HTMLWindow_iface_tids,
-    IHTMLWindow5_tid
+    HTMLWindow_init_dispex_info
 };
 
 static void *alloc_window(size_t size)
diff --git a/dlls/mshtml/mshtml_private.h b/dlls/mshtml/mshtml_private.h
index 04a1ccf49d2..412db241ee5 100644
--- a/dlls/mshtml/mshtml_private.h
+++ b/dlls/mshtml/mshtml_private.h
@@ -265,7 +265,7 @@ typedef struct {
     const dispex_static_data_vtbl_t *vtbl;
     const tid_t disp_tid;
     const tid_t* const iface_tids;
-    const tid_t additional_tid;
+    void (*init_info)(dispex_data_t*);
     dispex_data_t *data;
 } dispex_static_data_t;
 
@@ -317,6 +317,7 @@ void dispex_unlink(DispatchEx*) DECLSPEC_HIDDEN;
 void release_typelib(void) DECLSPEC_HIDDEN;
 HRESULT get_htmldoc_classinfo(ITypeInfo **typeinfo) DECLSPEC_HIDDEN;
 const dispex_static_data_vtbl_t *dispex_get_vtbl(DispatchEx*) DECLSPEC_HIDDEN;
+void dispex_info_add_interface(dispex_data_t*,tid_t) DECLSPEC_HIDDEN;
 
 typedef enum {
     DISPEXPROP_CUSTOM,