diff --git a/contrib/check-code.py b/contrib/check-code.py
--- a/contrib/check-code.py
+++ b/contrib/check-code.py
@@ -75,6 +75,7 @@ testpats = [
     (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"),
+    (r'do\s*true;\s*done', "don't use true as loop body, use sleep 0"),
   ],
   # warnings
   []
@@ -98,8 +99,6 @@ utestpats = [
     (uprefix + r'set -e', "don't use set -e"),
     (uprefix + r'\s', "don't indent commands, use > for continued lines"),
     (uprefixc + r'( *)\t', "don't use tabs to indent"),
-    (uprefixc + r'.*do\s*true;\s*done',
-     "don't use true as loop body, use sleep 0"),
   ],
   # warnings
   []
diff --git a/tests/test-bad-pull.t b/tests/test-bad-pull.t
--- a/tests/test-bad-pull.t
+++ b/tests/test-bad-pull.t
@@ -20,7 +20,7 @@
 
   $ python dumb.py 2> log &
   $ P=$!
-  $ while [ ! -f listening ]; do true; done
+  $ while [ ! -f listening ]; do sleep 0; done
   $ hg clone http://localhost:$HGPORT/foo copy2
   abort: HTTP Error 404: * (glob)
   [255]
diff --git a/tests/test-hgweb-raw.t b/tests/test-hgweb-raw.t
--- a/tests/test-hgweb-raw.t
+++ b/tests/test-hgweb-raw.t
@@ -20,7 +20,7 @@ Test raw style of hgweb
   $ cat hg.pid >> $DAEMON_PIDS
   $ ("$TESTDIR/get-with-headers.py" localhost:$HGPORT '/?f=a23bf1310f6e;file=sub/some%20%22text%22.txt;style=raw' content-type content-length content-disposition) >getoutput.txt
 
-  $ while kill `cat hg.pid` 2>/dev/null; do true; done
+  $ while kill `cat hg.pid` 2>/dev/null; do sleep 0; done
 
   $ cat getoutput.txt
   200 Script output follows
@@ -41,7 +41,7 @@ Test raw style of hgweb
 
   $ cat hg.pid >> $DAEMON_PIDS
   $ ("$TESTDIR/get-with-headers.py" localhost:$HGPORT '/?f=a23bf1310f6e;file=sub/some%20%22text%22.txt;style=raw' content-type content-length content-disposition) >getoutput.txt
-  $ while kill `cat hg.pid` 2>/dev/null; do true; done
+  $ while kill `cat hg.pid` 2>/dev/null; do sleep 0; done
 
   $ cat getoutput.txt
   200 Script output follows
diff --git a/tests/test-http-proxy.t b/tests/test-http-proxy.t
--- a/tests/test-http-proxy.t
+++ b/tests/test-http-proxy.t
@@ -9,7 +9,7 @@
   $ cat hg.pid >> $DAEMON_PIDS
   $ cd ..
   $ "$TESTDIR/tinyproxy.py" $HGPORT1 localhost >proxy.log 2>&1 </dev/null &
-  $ while [ ! -f proxy.pid ]; do true; done
+  $ while [ ! -f proxy.pid ]; do sleep 0; done
   $ cat proxy.pid >> $DAEMON_PIDS
 
 url for proxy, stream
diff --git a/tests/test-https.t b/tests/test-https.t
--- a/tests/test-https.t
+++ b/tests/test-https.t
@@ -233,12 +233,12 @@ Fingerprints
   $ hg -R copy-pull id https://127.0.0.1:$HGPORT/
   5fed3813f7f5
 
-  $ while kill `cat hg1.pid` 2>/dev/null; do true; done
+  $ while kill `cat hg1.pid` 2>/dev/null; do sleep 0; done
 
 Prepare for connecting through proxy
 
   $ "$TESTDIR/tinyproxy.py" $HGPORT1 localhost >proxy.log </dev/null 2>&1 &
-  $ while [ ! -f proxy.pid ]; do true; done
+  $ while [ ! -f proxy.pid ]; do sleep 0; done
   $ cat proxy.pid >> $DAEMON_PIDS
 
   $ echo "[http_proxy]" >> copy-pull/.hg/hgrc