diff --git a/lib/linguist/language.rb b/lib/linguist/language.rb
index 694ccf31..20241232 100644
--- a/lib/linguist/language.rb
+++ b/lib/linguist/language.rb
@@ -26,7 +26,11 @@ module Linguist
       @name_index[name.downcase]
     end
 
-    def self.find_by_extension(filename)
+    def self.find_by_extension(extension)
+      @extension_index[extension]
+    end
+
+    def self.find_by_filename(filename)
       basename = File.basename(filename)
 
       if basename[0] == ?.
@@ -37,7 +41,7 @@ module Linguist
         ext = basename
       end
 
-      @extension_index[ext]
+      find_by_extension(ext)
     end
 
     attr_reader :name, :extensions
diff --git a/test/test_language.rb b/test/test_language.rb
index 686486a7..c5d6e477 100644
--- a/test/test_language.rb
+++ b/test/test_language.rb
@@ -16,14 +16,20 @@ class TestLanguage < Test::Unit::TestCase
     ruby = Language['Ruby']
     assert_equal ruby, Language.find_by_extension('.rb')
     assert_equal ruby, Language.find_by_extension('rb')
-    assert_equal ruby, Language.find_by_extension('foo.rb')
-    assert_equal ruby, Language.find_by_extension('./foo.rb')
-    assert_equal ruby, Language.find_by_extension('foo/bar.rb')
+    assert_nil Language.find_by_extension('foo.rb')
+  end
 
-    # TODO: Review questionable usage
-    assert_equal ruby, Language.find_by_extension('Rakefile')
-    assert_equal ruby, Language.find_by_extension('vendor/Rakefile')
-    assert_equal ruby, Language.find_by_extension('./Rakefile')
+  def test_find_by_filename
+    ruby = Language['Ruby']
+    assert_equal ruby, Language.find_by_filename('.rb')
+    assert_equal ruby, Language.find_by_filename('rb')
+    assert_equal ruby, Language.find_by_filename('foo.rb')
+    assert_equal ruby, Language.find_by_filename('./foo.rb')
+    assert_equal ruby, Language.find_by_filename('foo/bar.rb')
+
+    assert_equal ruby, Language.find_by_filename('Rakefile')
+    assert_equal ruby, Language.find_by_filename('vendor/Rakefile')
+    assert_equal ruby, Language.find_by_filename('./Rakefile')
   end
 
   def test_name