diff --git a/lib/childprocess/unix/process.rb b/lib/childprocess/unix/process.rb
index bae5ecd..5b72a59 100644
--- a/lib/childprocess/unix/process.rb
+++ b/lib/childprocess/unix/process.rb
@@ -50,7 +50,8 @@ def wait
         if exited?
           exit_code
         else
-          _, status = ::Process.waitpid2 _pid
+          _, status = ::Process.waitpid2(@pid)
+
           set_exit_code(status)
         end
       end