diff --git a/ui/frame_comfort.py b/ui/frame_comfort.py
index 4f636e6..cb2002e 100644
--- a/ui/frame_comfort.py
+++ b/ui/frame_comfort.py
@@ -183,7 +183,8 @@ def current(s, now):
     out = dict(s)
     out['time'] = time.time()  # event age uses the Frame's clock, not the phone's
     out['remaining'] = max(0, max(s.get('deadline', now), (s.get('warned') or 0) + 60) - now) if s.get('active') else 0
-    if s.get('active') and now - (s.get('heartbeat') or s.get('started') or now) > 90:
+    beat = s.get('heartbeat', s.get('started', now))  # a hand-edited state may lack either
+    if s.get('active') and now - beat > 90:
         out['error'] = 'Session worker is not responding. Timer enforcement is unverified; cancel and start again.'
     return out