diff --git a/Documentation/diff-format.txt b/Documentation/diff-format.txt
index b426a14..97756ec 100644
--- a/Documentation/diff-format.txt
+++ b/Documentation/diff-format.txt
@@ -81,7 +81,7 @@ The "diff" formatting options can be customized via the
 environment variable 'GIT_DIFF_OPTS'.  For example, if you
 prefer context diff:
 
-      GIT_DIFF_OPTS=-c git-diff-index -p $(cat .git/HEAD)
+      GIT_DIFF_OPTS=-c git-diff-index -p HEAD
 
 
 2. When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
