diff --git a/src/evalfunc.c b/src/evalfunc.c
index 1257aa0..846a914 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -5959,6 +5959,10 @@
 	}
 	else if (STRICMP(name, "vim_starting") == 0)
 	    n = (starting != 0);
+	else if (STRICMP(name, "ttyin") == 0)
+	    n = mch_input_isatty();
+	else if (STRICMP(name, "ttyout") == 0)
+	    n = stdout_isatty;
 #ifdef FEAT_MBYTE
 	else if (STRICMP(name, "multi_byte_encoding") == 0)
 	    n = has_mbyte;