diff --git a/README.md b/README.md
index f56ebe6..a3635a6 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,10 @@ On OS X, it has a few disadvantages compared to Time Machine - in particular it
 
         0 */1 * * * if [[ -d /mnt/backup ]]; then rsync_tmbackup.sh /home /mnt/backup; fi 
 	
+* The use `flock` is recommended so that only one instance of the script runs at a given time:
+
+	flock -n /tmp/rsync_tmbackup.lock rsync_tmbackup.sh /home /mnt/backup
+	
 ## Exclude file
 
 An optional exclude file can be provided as a third parameter. It should be compatible with the `--exclude-from` parameter of rsync. See [this tutorial](https://sites.google.com/site/rsync2u/home/rsync-tutorial/the-exclude-from-option) for more information.