diff --git a/activesupport/lib/active_support/testing/parallelize_executor.rb b/activesupport/lib/active_support/testing/parallelize_executor.rb
index d59f25f1ec..88299db3c0 100644
--- a/activesupport/lib/active_support/testing/parallelize_executor.rb
+++ b/activesupport/lib/active_support/testing/parallelize_executor.rb
@@ -49,7 +49,7 @@ module ActiveSupport
         end
 
         def parallelized?
-          @parallelized
+          @parallelized if defined?(@parallelized)
         end
 
         def should_parallelize?