diff --git a/src/borg/repository.py b/src/borg/repository.py
index 422a514007..7a9707e534 100644
--- a/src/borg/repository.py
+++ b/src/borg/repository.py
@@ -287,6 +287,19 @@ def __init__(self, id, repo):
                 id = bin_to_hex(id)
             super().__init__(id, repo)
 
+    class PackNotFound(ErrorWithTraceback):
+        """Object with key {} is indexed to pack {}, but that whole pack is missing from repository {}."""
+
+        exit_mcode = 23
+
+        # a missing pack means the index is stale or more than one object was lost.
+        def __init__(self, id, pack_id, repo):
+            if isinstance(id, bytes):
+                id = bin_to_hex(id)
+            if isinstance(pack_id, bytes):
+                pack_id = bin_to_hex(pack_id)
+            super().__init__(id, pack_id, repo)
+
     class ParentPathDoesNotExist(Error):
         """The parent path of the repository directory [{}] does not exist."""
 
@@ -836,7 +849,7 @@ def get_many(self, ids, read_data=True, raise_missing=True):
                 reader = self._cached_pack_reader(entry.pack_id)
             except StoreObjectNotFound:
                 if raise_missing:
-                    raise self.ObjectNotFound(id_, str(self._location)) from None
+                    raise self.PackNotFound(id_, entry.pack_id, str(self._location)) from None
                 yield None
             else:
                 yield reader.read(entry.obj_offset, entry.obj_size)
diff --git a/src/borg/testsuite/repository_test.py b/src/borg/testsuite/repository_test.py
index be43d3de1b..4f09999b29 100644
--- a/src/borg/testsuite/repository_test.py
+++ b/src/borg/testsuite/repository_test.py
@@ -253,6 +253,25 @@ def test_get_many_missing_id_yields_none(repo_fixtures, request):
         assert result[2] == repository.get(H(2))
 
 
+def test_get_many_missing_pack_raises_pack_not_found(repo_fixtures, request):
+    # get_many raises PackNotFound when a chunk's index entry points to a pack that is not in the
+    # store; with raise_missing=False it yields None instead.
+    objects = [(H(i), fchunk(b"payload-%02d" % i, chunk_id=H(i))) for i in range(2)]
+    with get_repository_from_fixture(repo_fixtures, request) as repository:
+        repository._pack_writer.max_count = 2  # one pack: {H0, H1}
+        for chunk_id, chunk in objects:
+            repository.put(chunk_id, chunk)
+        repository.flush()
+        pack_id = repository.chunks[H(0)].pack_id
+        repository.store_delete("packs/" + bin_to_hex(pack_id))  # delete the pack, keep its index entry
+
+        with pytest.raises(Repository.PackNotFound):
+            list(repository.get_many([H(0)]))
+        with pytest.raises(Repository.PackNotFound):
+            list(repository.get_many([H(0), H(1)]))  # one id's pack missing in a batch
+        assert list(repository.get_many([H(0)], raise_missing=False)) == [None]  # raise_missing=False -> None
+
+
 def test_get_many_repeated_ids(repo_fixtures, request):
     # A dedup'd item repeats chunk ids, e.g. [A, A, B, C, B]. Each repeat returns the right bytes
     # and each pack is loaded once: the cached pack serves the later visits.