diff --git a/mendel-builder/Dockerfile b/mendel-builder/Dockerfile
index 4ae471b..84e4692 100644
--- a/mendel-builder/Dockerfile
+++ b/mendel-builder/Dockerfile
@@ -29,8 +29,8 @@
 
 RUN /bin/bash -c 'git clone https://gerrit.googlesource.com/gcompute-tools /opt/gcompute-tools'
 
-ADD --chown=root:root aptly.conf         /etc/aptly.conf
-ADD --chown=root:root gpg-agent.conf     /etc/gpg-agent.conf
+COPY --chown=root:root aptly.conf         /etc/aptly.conf
+COPY --chown=root:root gpg-agent.conf     /etc/gpg-agent.conf
 
 RUN /bin/bash -c 'apt-get clean'