diff --git a/files/swh-dar-backup b/files/swh-dar-backup
index 3c04937..b78eeb6 100755
--- a/files/swh-dar-backup
+++ b/files/swh-dar-backup
@@ -1,63 +1,63 @@
 #!/bin/bash
 #
 # swh-dar-backup: run a local backup with dar
 #
 # Copyright (c) 2015 Nicolas Dandrimont <nicolas@dandrimont.eu>
 #
 # This file is part of the swh-dar puppet module
 #
 
 set -e
 
 if [ $# -ne 1 ]; then
   echo "Usage: $0 <config file>"
   exit 2
 fi
 
 BACKUP_CONFIG="$1"
 
 . "$BACKUP_CONFIG"
 . "$BACKUP_INCLUDE"
 . "$BACKUP_EXCLUDE"
 
-if [ -f "$BACKUP_LOCK" ]; then
-  echo "Lockfile \`$BACKUP_LOCK' present, exiting"
+if [ -f "$BACKUP_LOCK" ] && kill -0 "$(cat "$BACKUP_LOCK")" 2>/dev/null; then
+  echo "Lockfile \`$BACKUP_LOCK' present and process still exists, exiting"
   exit 2
 fi
 
 trap "rm -f '$BACKUP_LOCK'" EXIT
 
-touch "$BACKUP_LOCK"
+echo $$ > "$BACKUP_LOCK"
 
 # Don't let people believe that they can fetch the current backup
 rm -f "$BACKUP_DONE"
 
 BACKUP_BASENAME="$BACKUP_STORAGE/$BACKUP_TITLE."
 BACKUP_PATH="$BACKUP_BASENAME$(TZ=UTC date +"%Y-%m-%dT%H:%M:%SZ")"
 
 DAR_OPTIONS=(
     -c
     "$BACKUP_PATH"
     -R
     "$BACKUP_BASE"
     "${BACKUP_INCLUDE_OPTIONS[@]}"
     # Include empty directories
     -D
     "${BACKUP_EXCLUDE_OPTIONS[@]}"
     "${BACKUP_OPTIONS[@]}"
 )
 
 # Do the backup
 /usr/bin/dar "${DAR_OPTIONS[@]}"
 
 # Touch the flag file
 touch "$BACKUP_DONE"
 
 # Prune old backups
 count=0
 ls -1t "$BACKUP_BASENAME"* | while read f; do
     ((count=count+1))
     if (( "$count" > $BACKUP_KEEP )); then
 	rm "$f";
     fi
 done