diff --git a/stackrc b/stackrc
index 19f5b53..ae71772 100644
--- a/stackrc
+++ b/stackrc
@@ -102,9 +102,19 @@
     source $RC_DIR/.localrc.password
 fi
 
-# Control whether Python 3 should be used.
+# Control whether Python 3 should be used at all.
 export USE_PYTHON3=$(trueorfalse False USE_PYTHON3)
 
+# Control whether Python 3 is enabled for specific services by the
+# base name of the directory from which they are installed. See
+# enable_python3_package to edit this variable and use_python3_for to
+# test membership.
+export ENABLED_PYTHON3_PACKAGES="nova,glance,cinder,uwsgi"
+
+# Explicitly list services not to run under Python 3. See
+# disable_python3_package to edit this variable.
+export DISABLED_PYTHON3_PACKAGES=""
+
 # When Python 3 is supported by an application, adding the specific
 # version of Python 3 to this variable will install the app using that
 # version of the interpreter instead of 2.7.