diff --git a/Dockerfile b/Dockerfile
index 4fe4f59..35c26b5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -21,8 +21,8 @@ ARG \
   UID=1000 \
   GID=1000
 
-RUN groupadd --gid ${GID} app \
-  && useradd --gid ${GID} --no-log-init --create-home --uid ${UID} app \
+RUN groupadd --gid "${GID}" app \
+  && useradd --gid "${GID}" --no-log-init --create-home --uid "${UID}" app \
   && mkdir -p /home/app/.cache/proxy_scraper_checker \
   && chown ${UID}:${GID} /home/app/.cache/proxy_scraper_checker