diff --git a/lib/sprockets/asset_attributes.rb b/lib/sprockets/asset_attributes.rb
index 9a07ee218..08eb4c418 100644
--- a/lib/sprockets/asset_attributes.rb
+++ b/lib/sprockets/asset_attributes.rb
@@ -69,7 +69,7 @@ def extensions
     #     # => ".js"
     #
     def format_extension
-      extensions.detect { |ext|
+      extensions.reverse.detect { |ext|
         @environment.mime_types(ext) && !@environment.engines(ext)
       }
     end
diff --git a/test/test_asset_attributes.rb b/test/test_asset_attributes.rb
index 1e97b0eb2..75f27409b 100644
--- a/test/test_asset_attributes.rb
+++ b/test/test_asset_attributes.rb
@@ -58,6 +58,8 @@ class TestAssetAttributes < Sprockets::TestCase
     assert_equal ".js", pathname("jquery.min.js").format_extension
     assert_equal ".js", pathname("jquery.tmpl.js").format_extension
     assert_equal ".js", pathname("jquery.tmpl.min.js").format_extension
+    assert_equal ".js", pathname("jquery.csv.js").format_extension
+    assert_equal ".js", pathname("jquery.csv.min.js").format_extension
 
     env = Sprockets::Environment.new
     env.register_engine '.ms', Class.new
@@ -77,6 +79,8 @@ class TestAssetAttributes < Sprockets::TestCase
     assert_equal [".erb"], pathname("jquery.js.erb").engine_extensions
     assert_equal [".erb"], pathname("jquery.min.js.erb").engine_extensions
     assert_equal [".coffee"], pathname("jquery.min.coffee").engine_extensions
+    assert_equal [".erb"], pathname("jquery.csv.min.js.erb").engine_extensions
+    assert_equal [".coffee", ".erb"], pathname("jquery.csv.min.js.coffee.erb").engine_extensions
 
     env = Sprockets::Environment.new
     env.register_engine '.ms', Class.new