diff --git a/rails-prod-Dockerfile b/rails-prod-Dockerfile
index 00c47e4..471cd64 100644
--- a/rails-prod-Dockerfile
+++ b/rails-prod-Dockerfile
@@ -23,6 +23,7 @@ EXPOSE 443
 #Cache gems so they don't install on every code change
 WORKDIR /tmp
 COPY Gemfile Gemfile
+COPY Gemfile.lock Gemfile.lock
 RUN bundle install --without test
 
 # Copy site into place.