diff --git a/python/lsst/ts/externalscripts/base_take_twilight_flats.py b/python/lsst/ts/externalscripts/base_take_twilight_flats.py
index 50f935eea..c29276a3a 100644
--- a/python/lsst/ts/externalscripts/base_take_twilight_flats.py
+++ b/python/lsst/ts/externalscripts/base_take_twilight_flats.py
@@ -444,6 +444,7 @@ async def take_twilight_flats(self):
                         {self.config.max_exp_time} s. Taking images with exposure \
                             time {self.config.max_exp_time}."
                 )
+                exp_time = self.config.max_exp_time
 
             if exp_time < self.config.min_exp_time:
                 self.log.warning(