diff --git a/src/kyupy/sdf.py b/src/kyupy/sdf.py
index 5314efb..f11e932 100644
--- a/src/kyupy/sdf.py
+++ b/src/kyupy/sdf.py
@@ -217,9 +217,9 @@ def parse(text):
     return Lark(GRAMMAR, parser="lalr", transformer=SdfTransformer()).parse(text)
 
 
-def load(file):
+def load(file) -> DelayFile:
     """Parses the contents of ``file`` and returns a :class:`DelayFile` object.
 
     Files with `.gz`-suffix are decompressed on-the-fly.
     """
-    return parse(readtext(file))
+    return parse(readtext(file)) # type: ignore