PVS-Studio warning V629 for Clang

void EmitVBR64(uint64_t Val, unsigned NumBits) {
  if ((uint32_t)Val == Val)
    return EmitVBR((uint32_t)Val, NumBits);

  uint64_t Threshold = 1U << (NumBits-1);
  ...
}

This suspicious code was found in Clang project by PVS-Studio static code analyzer.
Warning message is:
V629 Consider inspecting the '1U << (NumBits - 1)' expression. Bit shifting of the 32-bit value with a subsequent expansion to the 64-bit type. bitstreamwriter.h 173

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