diff --git a/lib/preprocessor.js b/lib/preprocessor.js
index 3e4b3af..9d515e9 100644
--- a/lib/preprocessor.js
+++ b/lib/preprocessor.js
@@ -1,8 +1,10 @@
-var istanbul = require('istanbul');
+var istanbul = require('istanbul'),
+    ibrik    = require('ibrik');
 
 var createCoveragePreprocessor = function(logger, basePath, reporters) {
   var log = logger.create('preprocessor.coverage');
-  var instrumenter = new istanbul.Instrumenter();
+  var jsInstrumenter = new istanbul.Instrumenter();
+  var coffeeInstrumenter = new ibrik.Instrumenter();
 
   // if coverage reporter is not used, do not preprocess the files
   if (reporters.indexOf('coverage') === -1) {
@@ -15,10 +17,14 @@ var createCoveragePreprocessor = function(logger, basePath, reporters) {
     log.debug('Processing "%s".', file.originalPath);
 
     var jsPath = file.originalPath.replace(basePath + '/', './');
+    var instrumenter = jsPath.match(/\.coffee$/) ? coffeeInstrumenter : jsInstrumenter;
+
     instrumenter.instrument(content, jsPath, function(err, instrumentedCode) {
       if(err) {
         log.error('%s\n  at %s', err.message, file.originalPath);
       }
+
+      file.path = file.path.replace(/\.coffee$/, '.js');
       done(instrumentedCode);
     });
   };
diff --git a/package.json b/package.json
index 73b3db4..b7f7acd 100644
--- a/package.json
+++ b/package.json
@@ -20,6 +20,7 @@
   "author": "SATO taichi <ryushi@gmail.com>",
   "dependencies": {
     "istanbul": "~0.1.41",
+    "ibrik":  "~0.0.4",
     "dateformat": "~1.0.6"
   },
   "peerDependencies": {
diff --git a/test/preprocessor.spec.coffee b/test/preprocessor.spec.coffee
index 7b527cc..59728b0 100644
--- a/test/preprocessor.spec.coffee
+++ b/test/preprocessor.spec.coffee
@@ -12,6 +12,12 @@ describe 'preprocessor', ->
   }
   '''
 
+  ORIGINAL_COFFEE_CODE = '''
+  if a
+    something()
+  else
+    other()
+  '''
 
   mockLogger = create: ->
     error: -> throw new Error(util.format.apply util, arguments)
@@ -50,3 +56,17 @@ describe 'preprocessor', ->
       vm.runInNewContext preprocessedCode, sandbox
       expect(sandbox.__coverage__).to.have.ownProperty './file.js'
       done()
+
+  it 'should preprocess the coffee code', (done) ->
+    process = createPreprocessor mockLogger, '/base/path', ['coverage', 'progress']
+    file = new File '/base/path/file.coffee'
+
+    process ORIGINAL_COFFEE_CODE, file, (preprocessedCode) ->
+      sandbox =
+        a: true
+        something: ->
+
+      vm.runInNewContext preprocessedCode, sandbox
+      expect(file.path).to.equal '/base/path/file.js'
+      expect(sandbox.__coverage__).to.have.ownProperty './file.coffee'
+      done()