diff --git a/src/PatchFileIndex.cc b/src/PatchFileIndex.cc
index 0fe841d4..0e7e4770 100644
--- a/src/PatchFileIndex.cc
+++ b/src/PatchFileIndex.cc
@@ -120,6 +120,7 @@ PatchFileIndex::PatchFileIndex(const string& root_dir)
           });
           new_metadata_cache_json->as_dict().emplace(
               relative_item_path, make_json_list(move(new_cache_item)));
+          should_write_metadata_cache = true;
 
         } else {
           // File was not modified and cache item was valid; just use the