diff --git a/software/slaprunner/software.cfg b/software/slaprunner/software.cfg
index 1d7be25774ae25c1c8e3d5fe6d47ed23e9de7893..3dcc9a176a903f09009c396ddb7c85b03ca897d7 100644
--- a/software/slaprunner/software.cfg
+++ b/software/slaprunner/software.cfg
@@ -6,6 +6,7 @@ extensions =
   slapos.rebootstrap
 
 parts =
+  libxslt
   eggs
   template
 
diff --git a/stack/flask.cfg b/stack/flask.cfg
index 86ded06fe6a77ebff008c42b9c4dbdda0ce35d25..f864cb6cfb881ac79caff2158018940b6e9f0761 100644
--- a/stack/flask.cfg
+++ b/stack/flask.cfg
@@ -1,9 +1,24 @@
 # Stack for Flask microframework: http://flask.pocoo.org/
 [buildout]
+extensions =
+  slapos.zcbworkarounds
+
 extends =
   ../component/python-2.7/buildout.cfg
   ../component/lxml-python/buildout.cfg
 
+# Use only quite well working sites.
+allow-hosts =
+  *.nexedi.org
+  *.python.org
+  *.sourceforge.net
+  dist.repoze.org
+  effbot.org
+  github.com
+  peak.telecommunity.com
+  psutil.googlecode.com
+  www.dabeaz.com
+
 parts =
   libxslt
   eggs