PVS-Studio warning V629 for UnrealEngine4

class FMallocBinned : public FMalloc
{
  ....
  /* Used to mask off the bits that have been used to
     lookup the indirect table */
  uint64 PoolMask;
  ....
  FMallocBinned(uint32 InPageSize, uint64 AddressLimit)
  {
    ....
    PoolMask = ( ( 1 << ( HashKeyShift - PoolBitShift ) ) - 1 );
    ....
  }
}

This suspicious code was found in UnrealEngine4 project by PVS-Studio static code analyzer.
Warning message is:
V629 Consider inspecting the '1 << (HashKeyShift - PoolBitShift)' expression. Bit shifting of the 32-bit value with a subsequent expansion to the 64-bit type. mallocbinned.h 800

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/