diff --git a/.dir-locals.el b/.dir-locals.el
index 341425bd56..a63b0cf4a2 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -2,4 +2,5 @@
 ((nil . ((c-basic-offset . 4)
          (indent-tabs-mode . nil)
          (c-file-style . "ellemtel")
-         (c-file-offsets . ((innamespace . 0))))))
+         (c-file-offsets . ((innamespace . 0)))
+         (show-trailing-whitespace . t))))