diff --git a/app/models/site.rb b/app/models/site.rb
index 638b3f47..5dee0b85 100644
--- a/app/models/site.rb
+++ b/app/models/site.rb
@@ -335,7 +335,10 @@ class Site < ApplicationRecord
 
   def jekyll
     run_in_path do
-      @jekyll ||= Jekyll::Site.new(configuration)
+      @jekyll ||=
+        Jekyll::Site.new(configuration).tap do |site|
+          site.reader = JekyllData::Reader.new(site) if site.theme
+        end
     end
   end
 
@@ -382,9 +385,6 @@ class Site < ApplicationRecord
       @configuration[unneeded] = [] if @configuration.key? unneeded
     end
 
-    # Eliminar el theme si no es una gema válida
-    @configuration.delete('theme') unless theme_available?
-
     # Si estamos usando nuestro propio plugin de i18n, los posts están
     # en "colecciones"
     locales.map(&:to_s).each do |i|
@@ -394,20 +394,6 @@ class Site < ApplicationRecord
     @configuration
   end
 
-  # Lista los nombres de las plantillas disponibles como gemas,
-  # tomándolas dinámicamente de las que agreguemos en el grupo :themes
-  # del Gemfile.
-  def available_themes
-    @available_themes ||= Bundler.load.current_dependencies.select do |gem|
-      gem.groups.include? :themes
-    end.map(&:name)
-  end
-
-  # Detecta si el tema actual es una gema
-  def theme_available?
-    available_themes.include? design&.gem
-  end
-
   # Devuelve el dominio actual
   def self.domain
     ENV.fetch('SUTTY', 'sutty.nl')
diff --git a/config/initializers/core_extensions.rb b/config/initializers/core_extensions.rb
index 66d2c92b..1516a43a 100644
--- a/config/initializers/core_extensions.rb
+++ b/config/initializers/core_extensions.rb
@@ -37,6 +37,13 @@ end
 #
 # TODO: Aplicar monkey patches en otro lado...
 module Jekyll
+  Site.class_eval do
+    def configure_theme
+      self.theme = nil
+      self.theme = Jekyll::Theme.new(config['theme'], self) unless config['theme'].nil?
+    end
+  end
+
   Reader.class_eval do
     # No necesitamos otros posts
     def retrieve_posts(_); end
@@ -69,6 +76,46 @@ module Jekyll
     end
   end
 
+  Theme.class_eval do
+    attr_reader :site
+
+    def initialize(name, site)
+      @name = name.downcase.strip
+      @site = site
+    end
+
+    def root
+      @root ||= begin
+        lockfile = Bundler::LockfileParser.new(File.read(site.in_source_dir('Gemfile.lock')))
+        spec = lockfile.specs.find do |spec|
+          spec.name == name
+        end
+
+        ruby_version = Gem::Version.new(RUBY_VERSION)
+        ruby_version.canonical_segments[2] = 0
+        base_path = Rails.root.join('_storage', 'gems', File.basename(site.source), 'ruby',
+                                    ruby_version.canonical_segments.join('.'))
+
+        File.realpath(
+          case spec.source
+          when Bundler::Source::Git
+            File.join(base_path, 'bundler', 'gems', spec.source.extension_dir_name)
+          when Bundler::Source::Rubygems
+            File.join(base_path, 'gems', spec.full_name)
+          end
+        )
+      end
+    end
+
+    def runtime_dependencies
+      []
+    end
+
+    private
+
+    def gemspec; end
+  end
+
   # No necesitamos los archivos de la plantilla
   ThemeAssetsReader.class_eval do
     def read; end