diff --git a/docs/commands.md b/docs/commands.md
index 77304431..9b147707 100644
--- a/docs/commands.md
+++ b/docs/commands.md
@@ -141,6 +141,7 @@ Navigate the quations.
         * `algorithms`
         * `database`
         * `shell`
+        * `concurrency`
     * by company (require plugin)
     * by topic (require plugin)
 * `-s` to show statistic counters of the output list.
diff --git a/lib/config.js b/lib/config.js
index 9fc26945..ed390f04 100644
--- a/lib/config.js
+++ b/lib/config.js
@@ -10,7 +10,8 @@ const DEFAULT_CONFIG = {
     categories: [
       'algorithms',
       'database',
-      'shell'
+      'shell',
+      'concurrency'
     ],
     langs: [
       'bash',
diff --git a/test/plugins/test_leetcode.js b/test/plugins/test_leetcode.js
index d4e7a3e9..7fa2363c 100644
--- a/test/plugins/test_leetcode.js
+++ b/test/plugins/test_leetcode.js
@@ -121,9 +121,13 @@ describe('plugin:leetcode', function() {
         .get('/api/problems/shell/')
         .replyWithFile(200, './test/mock/problems.json.20160911');
 
+      nock('https://leetcode.com')
+        .get('/api/problems/concurrency/')
+        .replyWithFile(200, './test/mock/problems.json.20160911');
+
       plugin.getProblems(function(e, problems) {
         assert.equal(e, null);
-        assert.equal(problems.length, 377 * 3);
+        assert.equal(problems.length, 377 * 4);
         done();
       });
     });
@@ -141,6 +145,10 @@ describe('plugin:leetcode', function() {
         .get('/api/problems/shell/')
         .replyWithFile(200, './test/mock/problems.json.20160911');
 
+      nock('https://leetcode.com')
+        .get('/api/problems/concurrency/')
+        .replyWithFile(200, './test/mock/problems.json.20160911');
+
       plugin.getProblems(function(e, problems) {
         assert.equal(e.message, 'unknown error');
         done();