diff --git a/spec/lite_spec_helper.rb b/spec/lite_spec_helper.rb
index 3ec491c01e..82824c54b5 100644
--- a/spec/lite_spec_helper.rb
+++ b/spec/lite_spec_helper.rb
@@ -19,7 +19,14 @@
 
 require 'support/spec_config'
 require 'mrss/lite_constraints'
-require "support/session_registry"
+
+if Gem::Version.new(Mongo::VERSION) < Gem::Version.new('2.18.0.alpha')
+  require "mrss/session_registry_legacy"
+else
+  require "mrss/session_registry"
+end
+
+Mrss.patch_mongo_for_session_registry
 
 unless SpecConfig.instance.ci?
   begin
diff --git a/spec/mongoid/query_cache_spec.rb b/spec/mongoid/query_cache_spec.rb
index 454d6dd7f0..80d32cfc1f 100644
--- a/spec/mongoid/query_cache_spec.rb
+++ b/spec/mongoid/query_cache_spec.rb
@@ -17,11 +17,11 @@
     # occur only within the scope of these tests.
     #
     # Other session leaks will be detected and addressed as part of RUBY-2391.
-    SessionRegistry.instance.clear_registry
+    Mrss::SessionRegistry.instance.clear_registry
   end
 
   after do
-    SessionRegistry.instance.verify_sessions_ended!
+    Mrss::SessionRegistry.instance.verify_sessions_ended!
   end
 
   let(:reset_legacy_qc_warning) do
diff --git a/spec/shared b/spec/shared
index dc4bbe242a..9b452a0ecd 160000
--- a/spec/shared
+++ b/spec/shared
@@ -1 +1 @@
-Subproject commit dc4bbe242a6022f707eb0a661dee5ead7e5849a3
+Subproject commit 9b452a0ecd0556e20cebc354fcfc44c911f0545d
diff --git a/spec/support/session_registry.rb b/spec/support/session_registry.rb
deleted file mode 100644
index 32f8aad1bb..0000000000
--- a/spec/support/session_registry.rb
+++ /dev/null
@@ -1,50 +0,0 @@
-require 'singleton'
-
-module Mongo
-  class Client
-    alias :get_session_without_tracking :get_session
-
-    def get_session(options = {})
-      get_session_without_tracking(options).tap do |session|
-        SessionRegistry.instance.register(session)
-      end
-    end
-  end
-
-  class Session
-    alias :end_session_without_tracking :end_session
-
-    def end_session
-      SessionRegistry.instance.unregister(self)
-      end_session_without_tracking
-    end
-  end
-end
-
-
-class SessionRegistry
-  include Singleton
-
-  def initialize
-    @registry = {}
-  end
-
-  def register(session)
-    @registry[session.session_id] = session if session
-  end
-
-  def unregister(session)
-    @registry.delete(session.session_id)
-  end
-
-  def verify_sessions_ended!
-    unless @registry.empty?
-      sessions = @registry.map { |_, session| session }
-      raise "Session registry contains live sessions: #{sessions.join(', ')}"
-    end
-  end
-
-  def clear_registry
-    @registry = {}
-  end
-end