diff --git a/buildout.cfg b/buildout.cfg
index 6a294cf..60ee4f4 100644
--- a/buildout.cfg
+++ b/buildout.cfg
@@ -1,5 +1,5 @@
 [buildout]
-extends = https://raw.githubusercontent.com/zopefoundation/Zope/master/versions.cfg
+extends = https://raw.githubusercontent.com/zopefoundation/Zope/4.x/versions.cfg
 develop = .
 parts = interpreter test