diff --git a/PFERD/crawler.py b/PFERD/crawler.py
index 9ec5991..f8cf091 100644
--- a/PFERD/crawler.py
+++ b/PFERD/crawler.py
@@ -273,6 +273,9 @@ class Crawler(ABC):
             with self._conductor.progress_bar(desc, total=total) as bar:
                 yield bar
 
+    def should_crawl(self, path: PurePath) -> bool:
+        return self._transformer.transform(path) is not None
+
     async def download(
             self,
             path: PurePath,
@@ -280,8 +283,12 @@ class Crawler(ABC):
             redownload: Optional[Redownload] = None,
             on_conflict: Optional[OnConflict] = None,
     ) -> Optional[AsyncContextManager[FileSink]]:
+        transformed_path = self._transformer.transform(path)
+        if transformed_path is None:
+            return None
+
         return await self._output_dir.download(
-            path, mtime, redownload, on_conflict)
+            transformed_path, mtime, redownload, on_conflict)
 
     async def cleanup(self) -> None:
         await self._output_dir.cleanup()
diff --git a/PFERD/crawlers/local.py b/PFERD/crawlers/local.py
index 99bc700..360a9a9 100644
--- a/PFERD/crawlers/local.py
+++ b/PFERD/crawlers/local.py
@@ -81,7 +81,8 @@ class LocalCrawler(Crawler):
 
             for child in path.iterdir():
                 pure_child = pure / child.name
-                tasks.append(self._crawl_path(child, pure_child))
+                if self.should_crawl(child):
+                    tasks.append(self._crawl_path(child, pure_child))
 
         await asyncio.gather(*tasks)
 
diff --git a/PFERD/transformer.py b/PFERD/transformer.py
index 84332df..fb47c60 100644
--- a/PFERD/transformer.py
+++ b/PFERD/transformer.py
@@ -292,4 +292,4 @@ class Transformer:
             else:
                 continue
 
-        return None
+        return path