diff --git a/devstack/plugin.sh b/devstack/plugin.sh
index 1ab6905f7..a23baf447 100644
--- a/devstack/plugin.sh
+++ b/devstack/plugin.sh
@@ -202,7 +202,9 @@ function configure_mongodb {
     pip_install pymongo
     if is_ubuntu; then
         install_package mongodb-server
-        echo "smallfiles = true" | sudo tee --append /etc/mongodb.conf > /dev/null
+        if ! grep -qF "smallfiles = true" /etc/mongodb.conf; then
+            echo "smallfiles = true" | sudo tee --append /etc/mongodb.conf > /dev/null
+        fi
         restart_service mongodb
     elif is_fedora; then
         install_package mongodb