diff --git a/conf/init/certs_install.sh b/conf/init/certs_install.sh
index 2ae929ac0..9f440d8a6 100755
--- a/conf/init/certs_install.sh
+++ b/conf/init/certs_install.sh
@@ -9,7 +9,7 @@ fi
 
 # Add extra trusted certificates (as a directory)
 if [ -d /conf/stack/extra_ca_certs ]; then
-  if test $(ls -A "/conf/stack/extra_ca_certs"); then
+  if test "$(ls -A "/conf/stack/extra_ca_certs")"; then
       echo "Installing extra certificates found in /conf/stack/extra_ca_certs directory"
       cp /conf/stack/extra_ca_certs/* /usr/local/share/ca-certificates/
       cat /conf/stack/extra_ca_certs/* >> /venv/lib/python2.7/site-packages/requests/cacert.pem