diff --git a/dulwich/objects.py b/dulwich/objects.py
index 3c90a3a3e..5e01dd7d4 100644
--- a/dulwich/objects.py
+++ b/dulwich/objects.py
@@ -536,7 +536,7 @@ def raw_length(self) -> int:
         """Returns the length of the raw string of this object."""
         return sum(map(len, self.as_raw_chunks()))
 
-    def sha(self) -> "HASH":
+    def sha(self) -> Union[FixedSha, "HASH"]:
         """The SHA1 object that is the name of this object."""
         if self._sha is None or self._needs_serialization:
             # this is a local because as_raw_chunks() overwrites self._sha
diff --git a/pyproject.toml b/pyproject.toml
index 1be439b84..1d72cf160 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -42,7 +42,7 @@ pgp = ["gpg"]
 paramiko = ["paramiko"]
 dev = [
     "ruff==0.8.4",
-    "mypy==1.13.0"
+    "mypy==1.14.0"
 ]
 
 [project.scripts]