diff --git a/Gemfile b/Gemfile
index f8ff1f4a..0b4f3d85 100644
--- a/Gemfile
+++ b/Gemfile
@@ -23,7 +23,7 @@ gem 'jquery-ui-rails' , '~>5.0.5'
 # always possible on all platforms
 # Alternatively use --without <group> arguments to bundler to not install that group
 gem "sqlite3", group: :sqlite
-gem "mysql2", "~> 0.5.2", group: :mysql
+gem "mysql2", "~> 0.5", group: :mysql
 
 gem "RedCloth"
 gem "sanitize", "~> 5.0"
@@ -49,6 +49,9 @@ gem 'chartjs-ror', :git => 'git://github.com/ZeiP/chartjs-ror.git'
 gem "bootstrap-sass", "3.4.1"
 gem "font-awesome-sass", "~> 4.5.0"
 
+# Type checking
+gem "sorbet-runtime"
+
 group :development do
   gem "spring"
   gem "yard"
@@ -57,6 +60,7 @@ group :development do
 
   gem "bullet"
   gem "rack-mini-profiler"
+  gem "sorbet"
 end
 
 group :development, :test do
diff --git a/Gemfile.lock b/Gemfile.lock
index b1b0b653..4304154d 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -236,6 +236,10 @@ GEM
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
+    sorbet (0.4.5133)
+      sorbet-static (= 0.4.5133)
+    sorbet-runtime (0.4.5133)
+    sorbet-static (0.4.5133-universal-darwin-14)
     spring (2.1.0)
     sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
@@ -294,7 +298,7 @@ DEPENDENCIES
   listen
   minitest-stub-const
   mocha
-  mysql2 (~> 0.5.2)
+  mysql2 (~> 0.5)
   paperclip
   puma (~> 4.1)
   rack-mini-profiler
@@ -308,6 +312,8 @@ DEPENDENCIES
   sass-rails (~> 5.0)
   selenium-webdriver (~> 3.142)
   simplecov
+  sorbet
+  sorbet-runtime
   spring
   sqlite3
   therubyracer
@@ -317,4 +323,4 @@ DEPENDENCIES
   yard
 
 BUNDLED WITH
-   2.0.1
+   2.0.2