diff --git a/.env.example b/.env.example
index a62e2b0a..f79ff3a4 100644
--- a/.env.example
+++ b/.env.example
@@ -1,3 +1,4 @@
+RAILS_GROUPS=assets
 DELEGATE=athshe.sutty.nl
 HAINISH=../haini.sh/haini.sh
 DATABASE=
diff --git a/Dockerfile b/Dockerfile
index 0b3253b4..ee6ba871 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,7 +2,7 @@
 # el mismo repositorio de trabajo.  Cuando tengamos CI/CD algunas cosas
 # como el tarball van a tener que cambiar porque ya vamos a haber hecho
 # un clone/pull limpio.
-FROM alpine:3.13.5 AS build
+FROM alpine:3.13.6 AS build
 MAINTAINER "f <f@sutty.nl>"
 
 ARG RAILS_MASTER_KEY
@@ -14,10 +14,10 @@ ENV SECRET_KEY_BASE solo_es_necesaria_para_correr_rake
 ENV RAILS_ENV production
 ENV RAILS_MASTER_KEY=$RAILS_MASTER_KEY
 
-RUN apk add --no-cache libxslt libxml2 tzdata ruby ruby-bundler ruby-json ruby-bigdecimal ruby-rake
+RUN apk add --no-cache libxslt libxml2 tzdata ruby ruby-json ruby-bigdecimal ruby-rake
 RUN apk add --no-cache postgresql-libs git yarn brotli libssh2 python3
 
-RUN test "2.7.3" = `ruby -e 'puts RUBY_VERSION'`
+RUN test "2.7.4" = `ruby -e 'puts RUBY_VERSION'`
 
 # https://github.com/rubygems/rubygems/issues/2918
 # https://gitlab.alpinelinux.org/alpine/aports/issues/10808
@@ -29,7 +29,7 @@ RUN cd /usr/lib/ruby/2.7.0 && patch -Np 0 -i /tmp/rubygems-platform-musl.patch
 RUN addgroup -g 82 -S www-data
 RUN adduser -s /bin/sh -G www-data -h /home/app -D app
 RUN install -dm750 -o app -g www-data /home/app/sutty
-RUN gem install --no-document bundler
+RUN gem install --no-document bundler:2.1.4
 
 # Empezamos con la usuaria app
 USER app
@@ -39,7 +39,8 @@ WORKDIR /home/app/sutty
 # Copiamos solo el Gemfile para poder instalar las gemas necesarias
 COPY --chown=app:www-data ./Gemfile .
 COPY --chown=app:www-data ./Gemfile.lock .
-RUN bundle config set no-cache 'true'
+RUN bundle config set no-cache true
+RUN bundle config set specific_platform true
 RUN bundle install --path=./vendor --without='test development'
 # Vaciar la caché
 RUN rm vendor/ruby/2.7.0/cache/*.gem
@@ -60,10 +61,6 @@ RUN mv ../sutty/.bundle ./.bundle
 # Instalar secretos
 COPY --chown=app:root ./config/credentials.yml.enc ./config/
 
-# Eliminar la necesidad de un runtime JS en producción, porque los
-# assets ya están pre-compilados.
-RUN sed -re "/(sassc|uglifier|bootstrap|coffee-rails)/d" -i Gemfile
-RUN bundle clean
 RUN rm -rf ./node_modules ./tmp/cache ./.git ./test ./doc
 # Eliminar archivos innecesarios
 USER root
@@ -71,7 +68,7 @@ RUN apk add --no-cache findutils
 RUN find /home/app/checkout/vendor/ruby/2.7.0 -maxdepth 3 -type d -name test -o -name spec -o -name rubocop | xargs -r rm -rf
 
 # Contenedor final
-FROM sutty/monit:latest
+FROM registry.nulo.in/sutty/monit:3.13.6
 ENV RAILS_ENV production
 
 # Pandoc
@@ -79,13 +76,13 @@ RUN echo 'http://dl-cdn.alpinelinux.org/alpine/edge/testing' >> /etc/apk/reposit
 
 # Instalar las dependencias, separamos la librería de base de datos para
 # poder reutilizar este primer paso desde otros contenedores
-RUN apk add --no-cache libxslt libxml2 tzdata ruby ruby-bundler ruby-json ruby-bigdecimal ruby-rake ruby-irb
+RUN apk add --no-cache libxslt libxml2 tzdata ruby ruby-json ruby-bigdecimal ruby-rake ruby-irb ruby-io-console ruby-etc
 RUN apk add --no-cache postgresql-libs libssh2 file rsync git jpegoptim vips
 RUN apk add --no-cache ffmpeg imagemagick pandoc tectonic oxipng jemalloc
 RUN apk add --no-cache git-lfs openssh-client patch
 
 # Chequear que la versión de ruby sea la correcta
-RUN test "2.7.3" = `ruby -e 'puts RUBY_VERSION'`
+RUN test "2.7.4" = `ruby -e 'puts RUBY_VERSION'`
 
 # https://github.com/rubygems/rubygems/issues/2918
 # https://gitlab.alpinelinux.org/alpine/aports/issues/10808
@@ -97,7 +94,7 @@ RUN apk add --no-cache patch && cd /usr/lib/ruby/2.7.0 && patch -Np 0 -i /tmp/ru
 # principal
 RUN apk add --no-cache yarn
 # Instalar foreman para poder correr los servicios
-RUN gem install --no-document --no-user-install bundler foreman
+RUN gem install --no-document --no-user-install bundler:2.1.4 foreman
 
 # Agregar el grupo del servidor web y la usuaria
 RUN addgroup -g 82 -S www-data
diff --git a/Gemfile b/Gemfile
index db06827d..981ce7fd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,13 +11,16 @@ gem 'dotenv-rails', require: 'dotenv/rails-now'
 gem 'rails', '~> 6'
 # Use Puma as the app server
 gem 'puma'
-# See https://github.com/rails/execjs#readme for more supported runtimes
-# gem 'therubyracer', platforms: :ruby
-# Use SCSS for stylesheets
-gem 'sassc-rails'
-# Use Uglifier as compressor for JavaScript assets
-gem 'uglifier', '>= 1.3.0'
-gem 'bootstrap', '~> 4'
+
+# Solo incluir las gemas cuando estemos en desarrollo o compilando los
+# assets.  No es necesario instalarlas en producción.
+#
+# XXX: Supuestamente Rails ya soporta RAILS_GROUPS, pero Bundler no.
+if ENV['RAILS_GROUPS']&.split(',')&.include? 'assets'
+  gem 'sassc-rails'
+  gem 'uglifier', '>= 1.3.0'
+  gem 'bootstrap', '~> 4'
+end
 
 # Turbolinks makes navigating your web application faster. Read more:
 # https://github.com/turbolinks/turbolinks
diff --git a/Makefile b/Makefile
index 592592bd..18914f43 100644
--- a/Makefile
+++ b/Makefile
@@ -48,7 +48,7 @@ help: always ## Ayuda
 	@echo -e "\nArgumentos:\n"
 	@grep -E "^[a-z\-]+ \?=.*##" Makefile | sed -re "s/(.*) \?=.*##(.*)/\1;\2/" | column -s ";" -t | sed -re "s/^([^ ]+) /\x1B[38;5;197m\1\x1B[0m/"
 
-assets: node_modules public/packs/manifest.json.br ## Compilar los assets
+assets: public/packs/manifest.json.br ## Compilar los assets
 
 test: always ## Ejecutar los tests
 	$(MAKE) rake args="test RAILS_ENV=test $(args)"