diff --git a/Gemfile b/Gemfile
index ff552f57..05771020 100644
--- a/Gemfile
+++ b/Gemfile
@@ -14,7 +14,7 @@ gem 'highline'
 gem 'jbuilder'
 gem 'jquery-rails'
 gem 'jquery-turbolinks'
-gem 'ims-lti', '1.1.10'
+gem 'ims-lti', '1.1.10' # version 1.1.13 will crash, because @provider.valid_request?(request) on lti.rb line 89 will return false.
 gem 'kramdown'
 gem 'newrelic_rpm'
 gem 'pg', '< 1.0', platform: :ruby
@@ -37,6 +37,7 @@ gem 'uglifier'
 gem 'will_paginate'
 gem 'tubesock'
 gem 'faye-websocket'
+gem 'eventmachine', '1.0.9.1' # explicitly added, this is used by faye-websocket, version 1.25 still has an error in eventmachine.rb:202: [BUG] Segmentation fault, which is not yet fixed and causes the whole ruby process to crash
 gem 'nokogiri'
 gem 'd3-rails'
 gem 'rest-client'
diff --git a/Gemfile.lock b/Gemfile.lock
index 254682cd..8b3c2dbc 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -124,8 +124,8 @@ GEM
       unf (>= 0.0.5, < 1.0.0)
     erubi (1.7.0)
     erubis (2.7.0)
-    eventmachine (1.2.5)
-    eventmachine (1.2.5-java)
+    eventmachine (1.0.9.1)
+    eventmachine (1.0.9.1-java)
     excon (0.60.0)
     execjs (2.7.0)
     factory_bot (4.8.2)
@@ -410,6 +410,7 @@ DEPENDENCIES
   d3-rails
   database_cleaner
   docker-api
+  eventmachine (= 1.0.9.1)
   factory_bot_rails
   faye-websocket
   forgery