diff --git a/PFERD/download_summary.py b/PFERD/download_summary.py
index 28d51b5..c8135de 100644
--- a/PFERD/download_summary.py
+++ b/PFERD/download_summary.py
@@ -40,9 +40,9 @@ class DownloadSummary:
         """
         Merges ourselves with the passed summary. Modifies this object, but not the passed one.
         """
-        self._new_files += summary.new_files
-        self._modified_files += summary.modified_files
-        self._deleted_files += summary.deleted_files
+        self._new_files = list(set(self._new_files + summary.new_files))
+        self._modified_files = list(set(self._modified_files + summary.modified_files))
+        self._deleted_files = list(set(self._deleted_files + summary.deleted_files))
 
     def add_deleted_file(self, path: Path) -> None:
         """