diff --git a/lib/linguist/languages.yml b/lib/linguist/languages.yml
index 51cb8aaa..5293f1c4 100644
--- a/lib/linguist/languages.yml
+++ b/lib/linguist/languages.yml
@@ -235,8 +235,9 @@ CoffeeScript:
   color: "#244776"
   aliases:
   - coffee
+  primary_extension: .coffee
   extensions:
-  - .coffee
+  - ._coffee
   filenames:
   - Cakefile
 
@@ -644,6 +645,7 @@ JavaScript:
   - node
   primary_extension: .js
   extensions:
+  - ._js
   - .bones
   - .jake
   - .js
diff --git a/test/test_language.rb b/test/test_language.rb
index b3f996d5..ed82a824 100644
--- a/test/test_language.rb
+++ b/test/test_language.rb
@@ -254,6 +254,11 @@ class TestLanguage < Test::Unit::TestCase
     assert_equal Language['PHP'], Language.find_by_extension('php5')
     assert_equal Language['PowerShell'], Language.find_by_extension('psm1')
     assert_equal Language['PowerShell'], Language.find_by_extension('ps1')
+
+    # Aliases for Streamline.js ( https://github.com/Sage/streamlinejs )
+    assert_equal Language['JavaScript'], Language.find_by_extension('_js')
+    assert_equal Language['CoffeeScript'], Language.find_by_extension('_coffee')
+
     assert_nil Language.find_by_extension('.nkt')
   end
 
@@ -345,6 +350,8 @@ class TestLanguage < Test::Unit::TestCase
     assert_equal '.pl', Language['Perl'].primary_extension
     assert_equal '.py', Language['Python'].primary_extension
     assert_equal '.rb', Language['Ruby'].primary_extension
+    assert_equal '.js', Language['JavaScript'].primary_extension
+    assert_equal '.coffee', Language['CoffeeScript'].primary_extension
 
     # This is a nasty requirement, but theres some code in GitHub that
     # expects this. Really want to drop this.