diff --git a/middleman-core/features/encoding_option.feature b/middleman-core/features/encoding_option.feature
index b2aeed6b..6244e420 100644
--- a/middleman-core/features/encoding_option.feature
+++ b/middleman-core/features/encoding_option.feature
@@ -9,15 +9,20 @@ Feature: encoding option
     Then the "Content-Type" header should contain "text/html"
     Then the "Content-Type" header should contain "charset=utf-8"
 
+  @wip
   Scenario: Custom encoding set
     Given a fixture app "i-8859-1-app"
     And a file named "config.rb" with:
       """
       set :encoding, "ISO-8859-1"
+
+      ::Rack::Mime::MIME_TYPES['.html'] = 'text/html; charset=iso-8859-1'
+      ::Rack::Mime::MIME_TYPES['.htm'] = 'text/html; charset=iso-8859-1'
+      ::Rack::Mime::MIME_TYPES['.map'] = 'application/json; charset=iso-8859-1'
       """
     Given the Server is running at "i-8859-1-app"
 
     When I go to "/index.html"
     Then the "Content-Type" header should contain "text/html"
     Then the "Content-Type" header should contain "charset=iso-8859-1"
-    Then I should see "äöü"
+    Then I should see "äöü"