diff --git a/ci/release-image/entrypoint.sh b/ci/release-image/entrypoint.sh
index f71df255d..16ae5a892 100755
--- a/ci/release-image/entrypoint.sh
+++ b/ci/release-image/entrypoint.sh
@@ -7,7 +7,7 @@ eval "$(fixuid -q)"
 
 if [ "${DOCKER_USER-}" ]; then
   USER="$DOCKER_USER"
-  if [ "$DOCKER_USER" != "$(whoami)" -a -z "$(id -u $DOCKER_USER 2>/dev/null)" ]; then
+  if [ "$DOCKER_USER" != "$(whoami)" -a -z "$(id -u "$DOCKER_USER" 2>/dev/null)" ]; then
     echo "$DOCKER_USER ALL=(ALL) NOPASSWD:ALL" | sudo tee -a /etc/sudoers.d/nopasswd > /dev/null
     # Unfortunately we cannot change $HOME as we cannot move any bind mounts
     # nor can we bind mount $HOME into a new home as that requires a privileged container.