diff --git a/spec/support/shell_out.rb b/spec/support/shell_out.rb
index 4417ac14b..4bb5b5202 100644
--- a/spec/support/shell_out.rb
+++ b/spec/support/shell_out.rb
@@ -2,6 +2,7 @@
 
 class ShellOut
   WaitTimeout = Class.new(StandardError)
+  PROCESS_EXIT = "[PROCESS EXIT]"
 
   def self.command(command, env: {}, &block)
     new.command(command, env: env, &block)
@@ -43,14 +44,14 @@ def command(command, env: {})
           Process.kill('TERM', pid)
           wait_thr.value
         rescue Errno::ESRCH
-          puts "Process already exited."
+          @output << PROCESS_EXIT
         end
       end
 
       stdout_future.value
       stderr_future.value
 
-      output
+      @output
     end
   end
 end