PVS-Studio warning V564 for OpenMW

enum Flags
{
  ....
  NoDuration = 0x4,
  ....
}

bool CastSpell::cast (const ESM::Ingredient* ingredient)
{
  ....
  if (!magicEffect->mData.mFlags & ESM::MagicEffect::NoDuration)
  ....
}

This suspicious code was found in OpenMW project by PVS-Studio static code analyzer.
Warning message is:
V564 The '&' operator is applied to bool type value. You've probably forgotten to include parentheses or intended to use the '&&' operator. openmw spellcasting.cpp 717

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/