diff --git a/Gemfile b/Gemfile
index 184a0f4..4dbe5bc 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,3 +5,4 @@ gem 'middleman-autoprefixer', '~> 2.7'
 gem 'tzinfo-data', platforms: [:mswin, :mingw, :jruby]
 gem 'wdm', '~> 0.1', platforms: [:mswin, :mingw]
 gem 'rake'
+gem 'webrick'
diff --git a/Gemfile.lock b/Gemfile.lock
index a81d376..5c64d97 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -97,6 +97,7 @@ GEM
       thread_safe (~> 0.1)
     uglifier (3.2.0)
       execjs (>= 0.3.0, < 3)
+    webrick (1.7.0)
 
 PLATFORMS
   ruby
@@ -107,6 +108,7 @@ DEPENDENCIES
   rake
   tzinfo-data
   wdm (~> 0.1)
+  webrick
 
 BUNDLED WITH
-   2.1.4
+   2.2.4
diff --git a/README.md b/README.md
index ab1c74f..0588a4c 100644
--- a/README.md
+++ b/README.md
@@ -17,8 +17,12 @@ It is using middleman.
 - `netlify` command v2
 - Environment variable `NETLIFY_AUTH_TOKEN`
 
+### Ruby
+
+- Execute `bundle install --path=vendor/bundle` at first
+
 ## Usefull commands
 
-- `middleman` for live preview during development
+- `bundle exec middleman` for live preview during development
 - `bundle exec rake build_site` when deploying
 - `bundle exec rake deploy_trans` when deploying https://translate.joinplu.me/
diff --git a/source/_nav.erb b/source/_nav.erb
index c4b3f7b..04c27be 100644
--- a/source/_nav.erb
+++ b/source/_nav.erb
@@ -10,7 +10,7 @@
        <a href="https://github.com/Plume-org/Plume">Source code</a>
     </li>
     <li>
-       <a href="https://riot.im/app/#/room/#plume:disroot.org">Chat room</a>
+       <a href="https://matrix.to/#/#plume-blog:matrix.org">Chat room</a>
     </li>
     <li>
        <a href="https://fediverse.blog/~/PlumeDev">Updates</a>