1 files changed, 3 insertions, 1 deletions
diff --git a/activesupport/lib/active_support/testing/isolation.rb b/activesupport/lib/active_support/testing/isolation.rb
index cdd6d5f49b..bec303f6ab 100644
--- a/activesupport/lib/active_support/testing/isolation.rb
+++ b/activesupport/lib/active_support/testing/isolation.rb
@@ -1,3 +1,5 @@
+require 'active_support/core_ext/load_error'
+
 module ActiveSupport
   module Testing
     class ProxyTestResult
@@ -107,4 +109,4 @@ if ENV['ISOLATION_TEST']
       super && test.method_name == ENV['ISOLATION_TEST']
     end
   end
-end
-\ No newline at end of file
+end