diff --git a/stackrc b/stackrc
index dcc0ce4..0d1880c 100644
--- a/stackrc
+++ b/stackrc
@@ -183,6 +183,14 @@
 # each services ${SERVICE}_ENFORCE_SCOPE variables
 ENFORCE_SCOPE=$(trueorfalse False ENFORCE_SCOPE)
 
+# Devstack supports the use of a global virtualenv. These variables enable
+# and disable this functionality as well as set the path to the virtualenv.
+# Note that the DATA_DIR is selected because grenade testing uses a shared
+# DATA_DIR but different DEST dirs and we don't want two sets of venvs,
+# instead we want one global set.
+GLOBAL_VENV=$(trueorfalse True GLOBAL_VENV)
+DEVSTACK_VENV=${DEVSTACK_VENV:-$DATA_DIR/venv}
+
 # Enable use of Python virtual environments.  Individual project use of
 # venvs are controlled by the PROJECT_VENV array; every project with
 # an entry in the array will be installed into the named venv.