diff --git a/mendel-builder/Dockerfile b/mendel-builder/Dockerfile
index 2998337..67f53b7 100644
--- a/mendel-builder/Dockerfile
+++ b/mendel-builder/Dockerfile
@@ -35,5 +35,5 @@
 
 RUN /bin/bash -c 'apt-get clean'
 
-VOLUME ['/var/lib/aptly', '/srv/aptly-publish-fs']
+VOLUME ["/var/lib/aptly", "/srv/aptly-publish-fs"]
 WORKDIR /var/lib/aptly