diff --git a/grow/routing/path_format.py b/grow/routing/path_format.py
index 7aba6ea6c..6af7bb9bc 100644
--- a/grow/routing/path_format.py
+++ b/grow/routing/path_format.py
@@ -138,7 +138,7 @@ def params_doc(self, path, doc):
             params['base'] = doc.base
         params['collection'] = structures.AttributeDict(
             base_path=doc.collection_base_path,
-            sub_path=doc.collection_base_path,
+            sub_path=doc.collection_sub_path,
             basename=doc.collection.basename,
             root=doc.collection.root)
         if '{category}' in path: