diff --git a/overviewer_core/tileset.py b/overviewer_core/tileset.py
index 1660348..6046ea4 100644
--- a/overviewer_core/tileset.py
+++ b/overviewer_core/tileset.py
@@ -757,8 +757,8 @@ class TileSet(object):
         #       Compare the last modified time of the chunk and tile. If the
         #       tile is older, mark it in a RendertileSet object as dirty.
 
-        for chunkx, chunkz, chunkmtime in self.regionset.iterate_newer_chunks(last_rendertime):
 
+        for chunkx, chunkz, chunkmtime in self.regionset.iterate_chunks() if markall else self.regionset.iterate_newer_chunks(last_rendertime): 
             chunkcount += 1
 
             if chunkmtime > max_chunk_mtime: