Index: /trunk/src/VBox/Frontends/VBoxManage/VBoxManageGuestCtrl.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VBoxManage/VBoxManageGuestCtrl.cpp	(revision 33775)
+++ /trunk/src/VBox/Frontends/VBoxManage/VBoxManageGuestCtrl.cpp	(revision 33776)
@@ -1298,4 +1298,5 @@
         ComPtr<IProgress> progress;
         CHECK_ERROR_BREAK(guest, UpdateGuestAdditions(Bstr(Utf8Source).raw(),
+                                                      0 /* Flags, not used. */,
                                                       progress.asOutParam()));
         rc = showProgress(progress);
Index: /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.cpp	(revision 33775)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.cpp	(revision 33776)
@@ -364,7 +364,7 @@
     CGuest guest = session().GetConsole().GetGuest();
 #ifdef DEBUG_andy
-    CProgress progressInstall = guest.UpdateGuestAdditions("c:\\Downloads\\VBoxGuestAdditions-r67158.iso");
+    CProgress progressInstall = guest.UpdateGuestAdditions("c:\\Downloads\\VBoxGuestAdditions_3.2.8.iso", 0);
 #else
-    CProgress progressInstall = guest.UpdateGuestAdditions(strSource);
+    CProgress progressInstall = guest.UpdateGuestAdditions(strSource, 0 /* Flags, not used. */);
 #endif
     bool fResult = guest.isOk();
Index: /trunk/src/VBox/Main/GuestImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/GuestImpl.cpp	(revision 33775)
+++ /trunk/src/VBox/Main/GuestImpl.cpp	(revision 33776)
@@ -2400,5 +2400,5 @@
 }
 
-STDMETHODIMP Guest::UpdateGuestAdditions(IN_BSTR aSource, IProgress **aProgress)
+STDMETHODIMP Guest::UpdateGuestAdditions(IN_BSTR aSource, ULONG aFlags, IProgress **aProgress)
 {
 #ifndef VBOX_WITH_GUEST_CONTROL
@@ -2408,4 +2408,7 @@
     CheckComArgOutPointerValid(aProgress);
 
+    if (aFlags != 0) /* Flags are not supported at the moment. */
+        return setError(E_INVALIDARG, tr("Unknown flags (%#x)"), aFlags);
+
     AutoCaller autoCaller(this);
     if (FAILED(autoCaller.rc())) return autoCaller.rc();
@@ -2445,7 +2448,8 @@
 
     if (SUCCEEDED(rc))
+    {
         /* Return progress to the caller. */
         progress.queryInterfaceTo(aProgress);
-
+    }
     return rc;
 #endif /* VBOX_WITH_GUEST_CONTROL */
Index: /trunk/src/VBox/Main/idl/VirtualBox.xidl
===================================================================
--- /trunk/src/VBox/Main/idl/VirtualBox.xidl	(revision 33775)
+++ /trunk/src/VBox/Main/idl/VirtualBox.xidl	(revision 33776)
@@ -7695,5 +7695,5 @@
   <interface
      name="IGuest" extends="$unknown"
-     uuid="5a4f265c-0c0e-495a-8ff6-7d68682e276b"
+     uuid="ded6983f-5c81-4bf9-90af-73f65fd9b728"
      wsmap="managed"
      >
@@ -7974,5 +7974,6 @@
       <param name="flags" type="unsigned long" dir="out">
         <desc>
-          Additional flags of process status (not used at the moment).
+          Additional flags of process status. Not used at the moment and
+          must be set to 0.
         </desc>
       </param>
@@ -8069,4 +8070,10 @@
         <desc>
           Path to the Guest Additions .ISO file to use for the upate.
+        </desc>
+      </param>
+      <param name="flags" type="unsigned long" dir="in">
+        <desc>
+          Additional flags for update process. Not used at the moment and
+          must be set to 0.
         </desc>
       </param>
Index: /trunk/src/VBox/Main/include/GuestImpl.h
===================================================================
--- /trunk/src/VBox/Main/include/GuestImpl.h	(revision 33775)
+++ /trunk/src/VBox/Main/include/GuestImpl.h	(revision 33776)
@@ -105,5 +105,5 @@
                                      ULONG *aMemTotal, ULONG *aMemFree, ULONG *aMemBalloon, ULONG *aMemShared, ULONG *aMemCache,
                                      ULONG *aPageTotal, ULONG *aMemAllocTotal, ULONG *aMemFreeTotal, ULONG *aMemBalloonTotal, ULONG *aMemSharedTotal);
-    STDMETHOD(UpdateGuestAdditions)(IN_BSTR aSource, IProgress **aProgress);
+    STDMETHOD(UpdateGuestAdditions)(IN_BSTR aSource, ULONG aFlags, IProgress **aProgress);
 
     // Public methods that are not in IDL (only called internally).