diff --git a/contrib/check-code.py b/contrib/check-code.py
index 72c6240a4b7d294f663007f6dcc5b61c7758f533_Y29udHJpYi9jaGVjay1jb2RlLnB5..e1f0305eabe43922c28d0f83376b5049299a6c39_Y29udHJpYi9jaGVjay1jb2RlLnB5 100755
--- a/contrib/check-code.py
+++ b/contrib/check-code.py
@@ -74,6 +74,7 @@
     (r'(\[|\btest\b).*-e ', "don't use 'test -e', use 'test -f'"),
     (r'^alias\b.*=', "don't use alias, use a function"),
     (r'if\s*!', "don't use '!' to negate exit status"),
+    (r'/dev/u?random', "don't use entropy, use /dev/zero"),
   ],
   # warnings
   []
diff --git a/tests/test-largefiles.t b/tests/test-largefiles.t
index 72c6240a4b7d294f663007f6dcc5b61c7758f533_dGVzdHMvdGVzdC1sYXJnZWZpbGVzLnQ=..e1f0305eabe43922c28d0f83376b5049299a6c39_dGVzdHMvdGVzdC1sYXJnZWZpbGVzLnQ= 100644
--- a/tests/test-largefiles.t
+++ b/tests/test-largefiles.t
@@ -815,7 +815,7 @@
 
 Test --normal flag
 
-  $ dd if=/dev/urandom bs=2k count=11k > new-largefile 2> /dev/null
+  $ dd if=/dev/zero bs=2k count=11k > new-largefile 2> /dev/null
   $ hg add --normal --large new-largefile
   abort: --normal cannot be used with --large
   [255]
@@ -945,7 +945,7 @@
   $ cd alice
   $ hg init pubrepo
   $ cd pubrepo
-  $ dd if=/dev/urandom bs=1k count=11k > a-large-file 2> /dev/null
+  $ dd if=/dev/zero bs=1k count=11k > a-large-file 2> /dev/null
   $ hg add --large a-large-file
   $ hg commit -m "Add a large file"
   Invoking status precommit hook