diff --git a/script/scan_guard.py b/script/scan_guard.py
index bcc165ef..d8e62af6 100644
--- a/script/scan_guard.py
+++ b/script/scan_guard.py
@@ -838,7 +838,7 @@ class ScanGuard(object):
     def mainloop(self):
         self._ringcurrent.pv.pend_io(timeout=0.01)
         #self.beam_ok = self.test or self.check_beam()
-        self.beam_ok = true
+        self.beam_ok = True
 
         self.test_start_seconds = time.time()
         self.running = True