diff --git a/src/kyupy/vcd.py b/src/kyupy/vcd.py
index 97e1501..8cfe8cd 100644
--- a/src/kyupy/vcd.py
+++ b/src/kyupy/vcd.py
@@ -154,7 +154,7 @@ GRAMMAR = r"""
     """
 
 
-def load(file, var_locs = lambda _: [], step_filter = lambda *_: True, s_len = None):
+def load(file, var_locs = lambda _: [], step_filter = lambda *_: True, s_len = None) -> VcdData:
     """Parses the contents of ``file`` as Verilog Change Dump (VCD).
 
     :param file: A file name or a file handle. Files with `.gz`-suffix are decompressed on-the-fly.