diff --git a/lisp/frame.el b/lisp/frame.el
index 04dd4abdf03..09738d1e2ed 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -2239,6 +2239,7 @@ See also `toggle-frame-maximized'."
         overline-margin
         line-prefix
         wrap-prefix
+        truncate-lines
         bidi-paragraph-direction
         bidi-display-reordering))