diff --git a/modules/puppetmaster/templates/puppet-merge.erb b/modules/puppetmaster/templates/puppet-merge.erb
index 845a998749..dd45030d78 100755
--- a/modules/puppetmaster/templates/puppet-merge.erb
+++ b/modules/puppetmaster/templates/puppet-merge.erb
@@ -21,7 +21,14 @@ lock() {
   if ! flock -xn $LOCKFD
   then
       trap EXIT
-      die "failed to lock, another puppet-merge running on this host?"
+      PSTREE=$(pstree -su $(fuser $LOCKFILE 2>/dev/null))
+      if [ $(echo "$PSTREE" | wc -l) -eq 1 ]
+      then
+        PSTREE="\nlocking process tree: $PSTREE"
+      else
+        PSTREE=""
+      fi
+      die "failed to lock, another puppet-merge running on this host?${PSTREE}"
   fi
 }