Text Services Framework AdviseSink failed for global compartment if application runs as SYSTEM user - com

Question

When I try to advise a ITfCompartmentEventSink for a global compartment in a process that has started as a SYSTEM user, the AdviseSink fails with E_FAIL. I tried with impersonating as normal user, but it doesn't seem to help.
And the compartment GetValue will succeed, but SetValue will also fail with E_FAIL.
However when the process is started as normal user, the AdviseSink works correctly.
The AdviseSink in following sample code also fails for SYSTEM user.
Windows-classic-samples\Samples\Win7Samples\winui\tsf\tsfcompart\monitor.cpp
So do I have to somehow set a security descriptor or initialize COM library with a particular option to make this work?
Thanks.
HRESULT CCompartmentMonitor::Initialize( const GUID *pguidCompartment,
PCOMPARTMENTMONITORPROC pCallback,
LPARAM lParam)
{
if(!IsEqualGUID(m_guidCompartment, GUID_NULL))
{
//Initialize() has already been called
return E_UNEXPECTED;
}
m_guidCompartment = *pguidCompartment;
m_pCallback = pCallback;
m_lParam = lParam;
HRESULT hr;
ITfThreadMgr *pThreadMgr;
//create a thread manager object
hr = CoCreateInstance(CLSID_TF_ThreadMgr,
NULL,
CLSCTX_INPROC_SERVER,
IID_ITfThreadMgr,
(void**)&pThreadMgr);
if(SUCCEEDED(hr))
{
ITfCompartmentMgr *pCompMgr;
//get the global compartment manager
hr = pThreadMgr->GetGlobalCompartment(&pCompMgr);
if(SUCCEEDED(hr))
{
//get the Speech UI compartment
hr = pCompMgr->GetCompartment(m_guidCompartment,
&m_pCompartment);
if(SUCCEEDED(hr))
{
ITfSource *pSource;
//install the advise sink
hr = m_pCompartment->QueryInterface(IID_ITfSource,
(LPVOID*)&pSource);
if(SUCCEEDED(hr))
{
hr = pSource->AdviseSink(IID_ITfCompartmentEventSink,
(ITfCompartmentEventSink*)this,
&m_dwCookie);
// AdviseSink fails with E_FAIL
}
//if something went wrong, release the member interface
if(FAILED(hr))
{
m_pCompartment->Release();
m_pCompartment = NULL;
}
}
//release the compartment manager
pCompMgr->Release();
}
//release the thread manager
pThreadMgr->Release();
}
return hr;
}