diff --git a/base-notebook/start.sh b/base-notebook/start.sh
index 4055dad9..63dc8db5 100755
--- a/base-notebook/start.sh
+++ b/base-notebook/start.sh
@@ -4,11 +4,11 @@
 
 set -e
 
-# The _log function is passed everything this script wants to log. It will
+# The _log function is used for everything this script wants to log. It will
 # always log errors and warnings, but can be silenced for other messages
 # by setting JUPYTER_DOCKER_STACKS_QUIET environment variable.
 _log () {
-    if [[ "$*" == "ERROR:"* ]] || [[ "$*" == "WARNING:"* ]] || [[ "$JUPYTER_DOCKER_STACKS_QUIET" == "" ]]; then
+    if [[ "$*" == "ERROR:"* ]] || [[ "$*" == "WARNING:"* ]] || [[ "${JUPYTER_DOCKER_STACKS_QUIET}" == "" ]]; then
         echo "$@"
     fi
 }