diff --git a/context/Dockerfile b/context/Dockerfile
index 607669aee75fbd44cfa25cd970348823c1cf9bff..0770adce2c8598aa734c3d303c8e141bd0e36404 100644
--- a/context/Dockerfile
+++ b/context/Dockerfile
@@ -14,4 +14,4 @@ RUN apt-get update \
 COPY s3-purge.sh /usr/local/bin/s3-purge
 COPY crontab /etc/cron.d/s3-purge
 
-CMD ["tail", "-f /dev/null"]
+CMD ["tail", "-f", "/dev/null"]