diff --git a/Gemfile b/Gemfile
index 591e908..df5651b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,4 +8,4 @@ gem 'rouge', '~> 1.8.0'
 gem 'redcarpet', '~> 3.2.2'
 
 gem 'rake', '~> 10.4.2'
-gem 'therubyracer', platforms: :ruby
+gem 'therubyracer', '~> 0.12.1', platforms: :ruby
diff --git a/Gemfile.lock b/Gemfile.lock
index 5080c7d..11aed00 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -130,4 +130,4 @@ DEPENDENCIES
   rake (~> 10.4.2)
   redcarpet (~> 3.2.2)
   rouge (~> 1.8.0)
-  therubyracer
+  therubyracer (~> 0.12.1)