diff --git a/doc/stim.pyi b/doc/stim.pyi
index 32d471208..941582719 100644
--- a/doc/stim.pyi
+++ b/doc/stim.pyi
@@ -1,5 +1,5 @@
 """Stim (Development Version): a fast quantum stabilizer circuit library."""
-# (This a stubs file describing the classes and methods in stim.)
+# (This is a stubs file describing the classes and methods in stim.)
 from __future__ import annotations
 from typing import overload, TYPE_CHECKING, List, Dict, Tuple, Any, Union, Iterable, Optional
 if TYPE_CHECKING: