@@ -1560,10 +1560,11 @@
 	AC_SUBST(OF_PROCESS_M, "OFProcess.m")
 	AC_DEFINE(OF_HAVE_PROCESSES, 1, [Whether we have processes])
 ])
 
 AC_CHECK_HEADERS_ONCE([complex.h sys/ioctl.h sys/ttycom.h])
+AC_CHECK_FUNCS(isatty)
 
 AC_CHECK_FUNC(pledge, [
 	AC_DEFINE(OF_HAVE_PLEDGE, 1, [Whether we have pledge()])
 ])