diff --git a/dokku b/dokku
index e692d1815..f1adf488e 100755
--- a/dokku
+++ b/dokku
@@ -92,7 +92,7 @@ case "$1" in
         # start the app
         DOCKER_ARGS=$(: | pluginhook docker-args $APP deploy)
         DOCKER_ARGS+=" -e DYNO=$PROC_TYPE "
-        DOCKER_ARGS+=" -e DYNO_TYPE_NUMBER=$PROC_TYPE.$CONTAINER_INDEX "
+        DOCKER_ARGS+=" -e DYNO_TYPE_NUMBER='$PROC_TYPE.$CONTAINER_INDEX' "
         DOCKER_ARGS+=$(: | pluginhook docker-args-deploy $APP)
         BIND_EXTERNAL=$(pluginhook bind-external-ip $APP)