diff --git a/reactos/include/psdk/hlguids.h b/reactos/include/psdk/hlguids.h
index 77bac3e4a94..7a45e668d86 100644
--- a/reactos/include/psdk/hlguids.h
+++ b/reactos/include/psdk/hlguids.h
@@ -25,5 +25,7 @@ DEFINE_GUID(CLSID_StdHlink,
     0x79eac9d0, 0xbaf9, 0x11ce, 0x8c, 0x82, 0x00, 0xaa,0x00,0x4b,0xa9,0x0b);
 DEFINE_GUID(CLSID_StdHlinkBrowseContext,
     0x79eac9d1, 0xbaf9, 0x11ce, 0x8c, 0x82, 0x00, 0xaa,0x00,0x4b,0xa9,0x0b);
+DEFINE_GUID(CLSID_IID_IExtensionServices,
+    0x79eac9cb, 0xbaf9, 0x11ce, 0x8c, 0x82, 0x00, 0xaa,0x00,0x4b,0xa9,0x0b);
 
 #endif
diff --git a/reactos/include/psdk/hlink.idl b/reactos/include/psdk/hlink.idl
index c59cd32098b..886acb36411 100644
--- a/reactos/include/psdk/hlink.idl
+++ b/reactos/include/psdk/hlink.idl
@@ -416,3 +416,25 @@ interface IHlinkFrame : IUnknown
         [in, unique] LPCWSTR pwzLocation, 
         [in, unique] LPCWSTR pwzFriendlyName);
 }
+
+/*****************************************************************************
+ *    IExtensionServices interface
+ */
+[
+    object,
+    uuid(79eac9cb-baf9-11ce-8c82-00aa004ba90b),
+    pointer_default(unique)
+]
+
+interface IExtensionServices: IUnknown
+{
+    typedef IExtensionServices *LPEXTENSIONSERVICES;
+
+    HRESULT SetAdditionalHeaders(
+        [in] LPCWSTR pwzAdditionalHeaders);
+
+    HRESULT SetAuthenticateData(
+        [in] HWND phwnd,
+        [in] LPCWSTR pwzUsername,
+        [in] LPCWSTR pwzPassword);
+}