PVS-Studio warning V547 for tesseract-ocr

uintmax_t streamtoumax(FILE* s, int base) {
  int d, c = 0;
  ....
  c = fgetc(s);
  if (c == 'x' && c == 'X') c = fgetc(s);
  ....
}

This suspicious code was found in tesseract-ocr project by PVS-Studio static code analyzer.
Warning message is:
V547 Expression 'c == 'x' && c == 'X'' is always false. Probably the '||' operator should be used here. libtesseract303 scanutils.cpp 135

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