diff --git a/lib/watcher.js b/lib/watcher.js
index 4befa8748..a6055bb70 100644
--- a/lib/watcher.js
+++ b/lib/watcher.js
@@ -4,6 +4,8 @@ var mm = require('minimatch');
 var helper = require('./helper');
 var log = require('./logger').create('watcher');
 
+var DIR_SEP = require('path').sep;
+
 // Get parent folder, that be watched (does not contain any special globbing character)
 var baseDirFromPattern = function(pattern) {
   return pattern.replace(/\/[^\/]*[\*\(].*$/, '') || '/';
@@ -32,7 +34,7 @@ var watchPatterns = function(patterns, watcher) {
   // watch only common parents, no sub paths
   pathsToWatch.forEach(function(path) {
     if (!pathsToWatch.some(function(p) {
-      return p !== path && path.substr(0, p.length) === p;
+      return p !== path && path.substr(0, p.length + 1) === p + DIR_SEP;
     })) {
       watcher.add(path);
       log.debug('Watching "%s"', path);
diff --git a/test/unit/watcher.spec.coffee b/test/unit/watcher.spec.coffee
index fea91dda1..55ed85a54 100644
--- a/test/unit/watcher.spec.coffee
+++ b/test/unit/watcher.spec.coffee
@@ -62,6 +62,12 @@ describe 'watcher', ->
       expect(chokidarWatcher.watchedPaths_).to.deep.equal ['/some']
 
 
+    it 'should watch a file matching subpath directory', ->
+      # regression #521
+      m.watchPatterns patterns('/some/test-file.js', '/some/test/**'), chokidarWatcher
+      expect(chokidarWatcher.watchedPaths_).to.deep.equal ['/some/test-file.js', '/some/test']
+
+
     it 'should not watch if watched false', ->
       m.watchPatterns [
         new config.Pattern('/some/*.js', true, true, false)