diff --git a/.dir-locals.el b/.dir-locals.el
index fd83da2315..58c5fdd1cd 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -1,3 +1,4 @@
 ((c-mode . ((c-file-style . "GNU")
             (c-basic-offset . 2)
-            (indent-tabs-mode . nil))))
+            (indent-tabs-mode . nil)
+            (show-trailing-whitespace . t))))