diff --git a/src/seismic_hazard_forecasting.py b/src/seismic_hazard_forecasting.py
index b980171..429fb37 100644
--- a/src/seismic_hazard_forecasting.py
+++ b/src/seismic_hazard_forecasting.py
@@ -679,7 +679,7 @@ verbose: {verbose}")
             logger.error(msg)
             raise Exception(msg)
         
-        if lambdas[0] == None:
+        if lambdas == None:
             msg = "Activity rate modeling was not selected and custom activity rate was not provided; cannot continue..."
             logger.error(msg)
             raise Exception(msg)