diff --git a/precise/base-0k/hooks/install b/precise/base-0k/hooks/install
index 124f15c..2561a9a 100755
--- a/precise/base-0k/hooks/install
+++ b/precise/base-0k/hooks/install
@@ -2,6 +2,8 @@
 
 set -eux # -x for verbose logging to juju debug-log
 
+DOCKER=${DOCKER:-}
+
 ## 0k git remote path
 GIT_0K_BASE=${GIT_0K_BASE:-"git.0k.io:/var/git"}