diff --git a/README b/README
index 9833019..5edba2e 100644
--- a/README
+++ b/README
@@ -78,7 +78,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*  touch           yes                          none
 #*  tr              yes                          none
 =*| true            yes                          none
-=*  tty             yes                          none
+=*| tty             yes                          none
 =*  uname           yes                          none
 #*  unexpand        yes                          none
 =*  uniq            yes                          none
diff --git a/tty.c b/tty.c
index acfec01..1c23bf4 100644
--- a/tty.c
+++ b/tty.c
@@ -20,8 +20,11 @@ main(int argc, char *argv[])
 		usage();
 	} ARGEND;
 
+	if (argc)
+		usage();
+
 	tty = ttyname(STDIN_FILENO);
 	puts(tty ? tty : "not a tty");
 
-	return tty ? 0 : 1;
+	return !tty;
 }