diff --git a/nengo_gui/page.py b/nengo_gui/page.py
index d90d9056..2a9b7433 100644
--- a/nengo_gui/page.py
+++ b/nengo_gui/page.py
@@ -119,7 +119,6 @@ def __init__(self, gui, filename, settings, reset_cfg=False):
         t = threading.Thread(target=self.runner)
         t.daemon = True
         t.start()
-        self.running_thread = t
 
     @property
     def sim(self):