diff --git a/spec/concurrent/executor/fixed_thread_pool_spec.rb b/spec/concurrent/executor/fixed_thread_pool_spec.rb
index 6c5ee43aa..a87eed8d1 100644
--- a/spec/concurrent/executor/fixed_thread_pool_spec.rb
+++ b/spec/concurrent/executor/fixed_thread_pool_spec.rb
@@ -208,7 +208,7 @@ module Concurrent
             end
           end
           latch.wait(1)
-        }.to raise_error
+        }.to raise_error(RejectedExecutionError)
       end
 
       # On discard, we'd expect no error, but also not all five results