diff --git a/Gemfile b/Gemfile
index f9f6e208..8ff54445 100644
--- a/Gemfile
+++ b/Gemfile
@@ -60,7 +60,7 @@ group :test do
   gem 'nyan-cat-formatter'
   gem 'rake'
   gem 'rspec-autotest'
-  gem 'rspec-rails', '~> 3.1.0'
+  gem 'rspec-rails'
   gem 'selenium-webdriver'
   gem 'simplecov', require: false
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index bde8fa1b..ef54d806 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -363,7 +363,7 @@ DEPENDENCIES
   rake
   ransack
   rspec-autotest
-  rspec-rails (~> 3.1.0)
+  rspec-rails
   rubocop
   rubocop-rspec
   rubytree
diff --git a/app/models/exercise.rb b/app/models/exercise.rb
index 6e7e090a..152d79bf 100644
--- a/app/models/exercise.rb
+++ b/app/models/exercise.rb
@@ -23,7 +23,7 @@ class Exercise < ActiveRecord::Base
   validates :token, presence: true, uniqueness: true
 
   def average_percentage
-    (average_score / maximum_score * 100).round if average_score
+    (average_score/ maximum_score * 100).round if average_score
   end
 
   def average_score
diff --git a/lib/docker_client.rb b/lib/docker_client.rb
index e5224236..f0799d8f 100644
--- a/lib/docker_client.rb
+++ b/lib/docker_client.rb
@@ -172,7 +172,12 @@ class DockerClient
   rescue Timeout::Error
     {status: :timeout}
   ensure
-    Concurrent::Future.execute { self.class.destroy_container(container) }
+    Concurrent::Future.execute {
+      #self.class.destroy_container(container)
+      FileUtils.rm_rf(local_workspace_path(container)) if local_workspace_path(container)
+      FileUtils.mkdir(local_workspace_path)
+      DockerContainerPool.return_container(container, @execution_environment)
+    }
   end
   private :send_command
 
diff --git a/lib/docker_container_pool.rb b/lib/docker_container_pool.rb
index c1d16c0a..3ca644df 100644
--- a/lib/docker_container_pool.rb
+++ b/lib/docker_container_pool.rb
@@ -20,6 +20,11 @@ class DockerContainerPool
     DockerClient.create_container(execution_environment)
   end
 
+  def self.return_container(container, execution_environment)
+    #container.start()
+    @containers[execution_environment.id].push(container)
+  end
+
   def self.get_container(execution_environment)
     if config[:active]
       @containers[execution_environment.id].try(:shift) || create_container(execution_environment)