--- /tmp/logrotate.orig	2013-07-29 14:04:58.843456488 +0000
+++ /etc/cron.daily/logrotate	2013-07-29 13:59:10.413591131 +0000
@@ -16,7 +16,11 @@
 fi
 
 if [ -x /usr/bin/ionice ]; then
-  CMD_LOGROTATE="/usr/bin/ionice -c ${IONICE_CLASS:-2} -n ${IONICE_PRIORITY:-7} ${CMD_LOGROTATE}"
+  IONICE_CMD="/usr/bin/ionice -c ${IONICE_CLASS:-2}"
+  if [ $IONICE_CLASS -ne 3 ]; then
+    IONICE_CMD="${IONICE_CMD} -n ${IONICE_PRIORITY:-7}"
+  fi
+  CMD_LOGROTATE="${IONICE_CMD} ${CMD_LOGROTATE}"
 fi
 
 ${CMD_LOGROTATE}