-CF_SUBST_IF(["$cf_cv_have_tcgetattr" = yes], HAVE_TCGETATTR, 1, 0)
-CF_SUBST_IF(["$ac_cv_header_termio_h" = yes], HAVE_TERMIO_H, 1, 0)
-CF_SUBST_IF(["$ac_cv_header_termios_h" = yes], HAVE_TERMIOS_H, 1, 0)
+CF_SUBST_IF(["x$cf_cv_have_tcgetattr" = xyes], HAVE_TCGETATTR, 1, 0)
+CF_SUBST_IF(["x$ac_cv_header_termio_h" = xyes], HAVE_TERMIO_H, 1, 0)
+CF_SUBST_IF(["x$ac_cv_header_termios_h" = xyes], HAVE_TERMIOS_H, 1, 0)