PVS-Studio warning V629 for xpdfwin

typedef signed long long S64;

SFIXED RFXSWF_QFIX(int zaehler, int nenner)
{
  S64 z = zaehler<<16;
  S64 a = z/(S64)nenner;
  return (SFIXED)a;
}

This suspicious code was found in xpdfwin project by PVS-Studio static code analyzer.
Warning message is:
V629 Consider inspecting the 'zaehler << 16' expression. Bit shifting of the 32-bit value with a subsequent expansion to the 64-bit type. swftools.c 37

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