diff --git a/pre-install.sh b/pre-install.sh
index 66ad255..dc98426 100644
--- a/pre-install.sh
+++ b/pre-install.sh
@@ -32,7 +32,7 @@ which pkg && { export pkgmgr='pkg' ; export pkgmgr_install=$pkgmgr' --yes instal
 if [ ! -z "$pkgmgr" ]; then
 	#upgrade the packages
 	echo "Info: $pkgmgr_upgrade_all"
-	$pkgmgr_upgrade_all
+	sh -c "$pkgmgr_upgrade_all"
 
 	#install git
 	echo "Info: $pkgmgr_install git"