diff --git a/lib/ecstatic/opts.js b/lib/ecstatic/opts.js
index b9738df..77d78a8 100644
--- a/lib/ecstatic/opts.js
+++ b/lib/ecstatic/opts.js
@@ -119,7 +119,6 @@ module.exports = function (opts) {
       'mime-Type',
       'mime-Types'
     ].some(function (k) {
-      k = k.toLowerCase();
       if (isDeclared(k)) {
         mimeTypes = opts[k];
         return true;
diff --git a/test/content-type.js b/test/content-type.js
index ea7af6c..4dafc89 100644
--- a/test/content-type.js
+++ b/test/content-type.js
@@ -84,7 +84,7 @@ test('throws when custom contentType .types file does not exist', function(t) {
   t.throws(
     setup.bind(null, {
       root: __dirname + '/public/',
-      'mime-types': 'this_file_does_not_exist.types'
+      mimeTypes: 'this_file_does_not_exist.types'
     })
   );