diff --git a/options/reconstruction.py b/options/reconstruction.py
index 0537fcaa807ae139cc544e74040dde0f69b48013..33e4c31fa70245ea9b93b8552a0e3789c1ebe8e5 100644
--- a/options/reconstruction.py
+++ b/options/reconstruction.py
@@ -40,7 +40,7 @@ print(calib_data)
 
 # input calorimeter DAQ info
 calo_daq = {}
-with open('config/calo_digi_{}.json'.format('detector_version')) as f:
+with open('config/calo_digi_{}.json'.format(detector_version)) as f:
     calo_config = json.load(f)
     ## add proper ADC capacity based on bit depth
     for sys in calo_config: