PVS-Studio warning V556 for Source SDK

enum PhysGunPickup_t
{
  PICKED_UP_BY_CANNON,
  PUNTED_BY_CANNON,
  PICKED_UP_BY_PLAYER, // Picked up by +USE, not physgun.
};

enum PhysGunDrop_t
{
  DROPPED_BY_PLAYER,
  THROWN_BY_PLAYER,
  DROPPED_BY_CANNON,
  LAUNCHED_BY_CANNON,
};

void CBreakableProp::OnPhysGunDrop(...., PhysGunDrop_t Reason)
{
  ....
  if( Reason == PUNTED_BY_CANNON )
  {
    PlayPuntSound();
  }
  ....
}

This suspicious code was found in Source SDK project by PVS-Studio static code analyzer.
Warning message is:
V556 The values of different enum types are compared: Reason == PUNTED_BY_CANNON. Server (HL2) props.cpp 1520

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/