PVS-Studio warning V601 for Micro-Manager

#define DEVICE_OK   0
#define DEVICE_ERR  1 // generic, undefined error
#define DEVICE_INVALID_PROPERTY  2

int MM::PropertyCollection::RegisterAction(
  const char* pszName, MM::ActionFunctor* fpAct)
{
  MM::Property* pProp = Find(pszName);
  if (!pProp)
    return DEVICE_INVALID_PROPERTY;
  pProp->RegisterAction(fpAct);
  return true;
}

This suspicious code was found in Micro-Manager project by PVS-Studio static code analyzer.
Warning message is:
V601 The 'true' value is implicitly casted to the integer type. Property.cpp 464

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/