diff --git a/src/Mmax.py b/src/Mmax.py
index 4a41ab1..3b747b6 100644
--- a/src/Mmax.py
+++ b/src/Mmax.py
@@ -206,7 +206,8 @@ def main(Input_catalog, Input_injection_rate, time_win_in_hours, time_step_in_ho
         Feat_dic['Param'][0]['C'] = C
 
     if f_indx in [0,1,2,4]:
-        Feat_dic['Param'][0]['b_method'] = b_method
+        if not b_method:
+            raise ValueError("Please chose an option for b-value")
 
     if f_indx in [0,4]:
         for cl_i in cl: