diff --git a/chellow/e/hh_parser_df2.py b/chellow/e/hh_parser_df2.py
index 84b7587bf..3927d8aae 100644
--- a/chellow/e/hh_parser_df2.py
+++ b/chellow/e/hh_parser_df2.py
@@ -79,12 +79,13 @@ def __next__(self):
                         raise BadRequest("Problem parsing the value: " + fields[2])
                     status = fields[3][-1]
 
+                    mpan_core = self.core
                     if self.core in self.mpan_map:
                         mapping = self.mpan_map[self.core]
                         if mapping["from"] <= start_date <= mapping["to"]:
-                            self.core = mapping["mpan"]
+                            mpan_core = mapping["mpan"]
 
-                            if self.core is None:
+                            if mpan_core is None:
                                 msg = f"The MPAN core {self.core} has been ignored"
                                 if len(self.messages) == 0 or self.messages[-1] != msg:
                                     self.messages.append(