c-mode single quote fontification

Question

I just noticed that single quotes are being font-locked with warning face, throwing off fontification of the entire buffer. Does anyone know why this is is happening? For example,

#include <stdio.h>

int main(int argc, char *argv[]) {

  if ( getc( stdin ) == '\n' )
               //why is ^ getting font-lock-warning-face?
    ;

  return 0;
}

Version info: emacs 26.0.50, semantic version 2.2. Started with emacs -Q, then enabling semantic mode, M-x semantic-mode in the buffer.