diff --git a/src/c3nav/mapdata/utils/cache/maphistory.py b/src/c3nav/mapdata/utils/cache/maphistory.py
index 72f3cd18..41335a3b 100644
--- a/src/c3nav/mapdata/utils/cache/maphistory.py
+++ b/src/c3nav/mapdata/utils/cache/maphistory.py
@@ -12,9 +12,10 @@ from c3nav.mapdata.utils.cache import GeometryIndexed
 class MapHistory(GeometryIndexed):
     # metadata format:
     # 2 bytes (uint16): number of updates
-    # n uptates times:
+    # n updates times:
     #     4 bytes (uint32): update id
     #     4 bytes (uint32): timestamp
+    # each uint16 cell contains the index of the newest update
     dtype = np.uint16
     variant_id = 1
 
diff --git a/src/c3nav/mapdata/utils/cache/maprestriction.py b/src/c3nav/mapdata/utils/cache/maprestriction.py
new file mode 100644
index 00000000..e69de29b