diff --git a/utils.py b/utils.py
index 1a60f6d..9b8a5e7 100644
--- a/utils.py
+++ b/utils.py
@@ -339,7 +339,8 @@ def identify_matching_ids(self,df_raw,res_id_list_full, bam_pgn):
         if self.tp_type == "j1939":
             df_raw_pgns = df_raw["ID"].apply(self.calculate_pgn)
             df_raw_match = df_raw_pgns.isin(res_id_list_full)
-            res_id_list = res_id_list_full.remove(bam_pgn)
+            res_id_list = res_id_list_full.copy() 
+            res_id_list.remove(bam_pgn)
             if type(res_id_list) is not list:
                 res_id_list = [res_id_list]
         elif self.tp_type == "uds":