diff --git a/doc/api/tty.md b/doc/api/tty.md
index 5d15addf39bec4..dbebbb77735797 100644
--- a/doc/api/tty.md
+++ b/doc/api/tty.md
@@ -245,6 +245,7 @@ added: v0.5.8
 -->
 
 * `fd` {number} A numeric file descriptor
+* Returns: {boolean}
 
 The `tty.isatty()` method returns `true` if the given `fd` is associated with
 a TTY and `false` if it is not, including whenever `fd` is not a non-negative