diff --git a/buildUpgradePackages.sh b/buildUpgradePackages.sh
index f19cdc4..ea43b90 100755
--- a/buildUpgradePackages.sh
+++ b/buildUpgradePackages.sh
@@ -1,6 +1,11 @@
 #!/usr/bin/env bash
 PKGDIR="/usr/portage/packages"
 
+if [[ $(pgrep -f -c $(basename $0)) -gt 1 ]] ; then
+      echo other instance still running
+      exit 1
+fi
+
 for atom in $(emerge -uDN --pretend --quiet world | grep ^'\[ebuild' | sed -e 's/.* \b\([a-z0-9\-]\+\/[\_A-Za-z\.0-9\-]\+\)\b.*/\1/g');
 do
   if [[ ! -f "$PKGDIR/$atom.tbz2" ]]