diff --git a/dlls/mshtml/htmlevent.c b/dlls/mshtml/htmlevent.c
index 2353d95c0d8..c037709b603 100644
--- a/dlls/mshtml/htmlevent.c
+++ b/dlls/mshtml/htmlevent.c
@@ -1418,10 +1418,35 @@ static HRESULT WINAPI DOMMouseEvent_initMouseEvent(IDOMMouseEvent *iface, BSTR t
         IEventTarget *related_target)
 {
     DOMEvent *This = impl_from_IDOMMouseEvent(iface);
-    FIXME("(%p)->(%s %x %x %p %d %d %d %d %d %x %x %x %x %u %p)\n", This, debugstr_w(type),
+    nsAString type_str;
+    nsresult nsres;
+    HRESULT hres;
+
+    TRACE("(%p)->(%s %x %x %p %d %d %d %d %d %x %x %x %x %u %p)\n", This, debugstr_w(type),
           can_bubble, cancelable, view, detail, screen_x, screen_y, client_x, client_y,
           ctrl_key, alt_key, shift_key, meta_key, button, related_target);
-    return E_NOTIMPL;
+
+    if(This->target) {
+        TRACE("called on already dispatched event\n");
+        return S_OK;
+    }
+
+    hres = IDOMEvent_initEvent(&This->IDOMEvent_iface, type, can_bubble, cancelable);
+    if(FAILED(hres))
+        return hres;
+
+    nsAString_InitDepend(&type_str, type);
+    nsres = nsIDOMMouseEvent_InitMouseEvent(This->mouse_event, &type_str, can_bubble, cancelable,
+                                            NULL /* FIXME */, detail, screen_x, screen_y,
+                                            client_x, client_y, ctrl_key, alt_key, shift_key,
+                                            meta_key, button, NULL /* FIXME */);
+    nsAString_Finish(&type_str);
+    if(NS_FAILED(nsres)) {
+        FIXME("InitMouseEvent failed: %08x\n", nsres);
+        return E_FAIL;
+    }
+
+    return S_OK;
 }
 
 static HRESULT WINAPI DOMMouseEvent_getModifierState(IDOMMouseEvent *iface, BSTR key,