diff --git a/lib/linguist/language.rb b/lib/linguist/language.rb
index 85e3426c..a06c59f0 100644
--- a/lib/linguist/language.rb
+++ b/lib/linguist/language.rb
@@ -2,6 +2,8 @@ require 'escape_utils'
 require 'pygments'
 require 'yaml'
 
+require 'linguist/sample'
+
 module Linguist
   # Language names that are recognizable by GitHub. Defined languages
   # can be highlighted, searched and listed under the Top Languages page.
@@ -444,10 +446,25 @@ module Linguist
     end
   end
 
+  extensions = Sample.extensions
   popular = YAML.load_file(File.expand_path("../popular.yml", __FILE__))
 
   YAML.load_file(File.expand_path("../languages.yml", __FILE__)).each do |name, options|
-    Language.create(
+    aliases = [name.downcase.gsub(/\s/, '-') ] + (options[:aliases] || [])
+    options['extensions'] ||= []
+    aliases.each do |name|
+      if extnames = extensions[name]
+        extnames.each do |extname|
+          if !options['extensions'].include?(extname)
+            options['extensions'] << extname
+          else
+            warn "#{name} #{extname.inspect} is already defined in samples/. Remove from languages.yml."
+          end
+        end
+      end
+    end
+
+    lang = Language.create(
       :name              => name,
       :color             => options['color'],
       :type              => options['type'],
@@ -457,7 +474,7 @@ module Linguist
       :group_name        => options['group'],
       :searchable        => options.key?('searchable') ? options['searchable'] : true,
       :search_term       => options['search_term'],
-      :extensions        => options['extensions'],
+      :extensions        => options['extensions'].sort,
       :primary_extension => options['primary_extension'],
       :overrides         => options['overrides'],
       :filenames         => options['filenames'],
diff --git a/lib/linguist/sample.rb b/lib/linguist/sample.rb
index 4b838626..096a9cba 100644
--- a/lib/linguist/sample.rb
+++ b/lib/linguist/sample.rb
@@ -1,3 +1,5 @@
+require 'set'
+
 module Linguist
   # Model for accessing classifier training data.
   module Sample
@@ -27,6 +29,22 @@ module Linguist
       nil
     end
 
+    # Get all extensions listed in samples/
+    #
+    # Returns Hash of sample language keys with a Set of extension
+    # Strings.
+    def self.extensions
+      extensions = {}
+      each do |sample|
+        extname = File.extname(sample[:path])
+        # TODO: For now skip empty extnames
+        next if extname == ""
+        extensions[sample[:language]] ||= Set.new
+        extensions[sample[:language]] << extname
+      end
+      extensions
+    end
+
     # Public: Build Classifier from all samples.
     #
     # Returns trained Classifier.