diff --git a/Dockerfile b/Dockerfile
index 4757646..c3eff79 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -14,8 +14,7 @@ ENV LANG=C.UTF-8 \
   BUNDLE_JOBS=4 \
   BUNDLE_RETRY=3
   
-RUN gem update --system
-RUN gem install bundler
+RUN gem update --system && gem install bundler
 
 WORKDIR /usr/src/app
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 7c4810b..8d2b238 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -113,7 +113,7 @@ GEM
     jbuilder (2.11.5)
       actionview (>= 5.0.0)
       activesupport (>= 5.0.0)
-    loofah (2.14.0)
+    loofah (2.15.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
@@ -235,7 +235,7 @@ GEM
       childprocess (>= 0.5, < 5.0)
       rexml (~> 3.2, >= 3.2.5)
       rubyzip (>= 1.2.2)
-    sprockets (4.0.2)
+    sprockets (4.0.3)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)
     sprockets-rails (3.4.2)