diff --git a/.ci/requirements-mypy.txt b/.ci/requirements-mypy.txt
index 23792281b15..47fc6439994 100644
--- a/.ci/requirements-mypy.txt
+++ b/.ci/requirements-mypy.txt
@@ -5,6 +5,7 @@ ipython
 numpy
 packaging
 pytest
+sphinx
 types-defusedxml
 types-olefile
 types-setuptools
diff --git a/docs/example/DdsImagePlugin.py b/docs/example/DdsImagePlugin.py
index 2a2a0ba2961..caa852b1fe1 100644
--- a/docs/example/DdsImagePlugin.py
+++ b/docs/example/DdsImagePlugin.py
@@ -14,6 +14,7 @@
 
 import struct
 from io import BytesIO
+from typing import IO
 
 from PIL import Image, ImageFile
 
@@ -94,26 +95,26 @@
 DXT5_FOURCC = 0x35545844
 
 
-def _decode565(bits):
+def _decode565(bits: int) -> tuple[int, int, int]:
     a = ((bits >> 11) & 0x1F) << 3
     b = ((bits >> 5) & 0x3F) << 2
     c = (bits & 0x1F) << 3
     return a, b, c
 
 
-def _c2a(a, b):
+def _c2a(a: int, b: int) -> int:
     return (2 * a + b) // 3
 
 
-def _c2b(a, b):
+def _c2b(a: int, b: int) -> int:
     return (a + b) // 2
 
 
-def _c3(a, b):
+def _c3(a: int, b: int) -> int:
     return (2 * b + a) // 3
 
 
-def _dxt1(data, width, height):
+def _dxt1(data: IO[bytes], width: int, height: int) -> bytes:
     # TODO implement this function as pixel format in decode.c
     ret = bytearray(4 * width * height)
 
@@ -151,7 +152,7 @@ def _dxt1(data, width, height):
     return bytes(ret)
 
 
-def _dxtc_alpha(a0, a1, ac0, ac1, ai):
+def _dxtc_alpha(a0: int, a1: int, ac0: int, ac1: int, ai: int) -> int:
     if ai <= 12:
         ac = (ac0 >> ai) & 7
     elif ai == 15:
@@ -175,7 +176,7 @@ def _dxtc_alpha(a0, a1, ac0, ac1, ai):
     return alpha
 
 
-def _dxt5(data, width, height):
+def _dxt5(data: IO[bytes], width: int, height: int) -> bytes:
     # TODO implement this function as pixel format in decode.c
     ret = bytearray(4 * width * height)
 
@@ -211,7 +212,7 @@ class DdsImageFile(ImageFile.ImageFile):
     format = "DDS"
     format_description = "DirectDraw Surface"
 
-    def _open(self):
+    def _open(self) -> None:
         if not _accept(self.fp.read(4)):
             msg = "not a DDS file"
             raise SyntaxError(msg)
@@ -242,19 +243,20 @@ def _open(self):
         elif fourcc == b"DXT5":
             self.decoder = "DXT5"
         else:
-            msg = f"Unimplemented pixel format {fourcc}"
+            msg = f"Unimplemented pixel format {repr(fourcc)}"
             raise NotImplementedError(msg)
 
         self.tile = [(self.decoder, (0, 0) + self.size, 0, (self.mode, 0, 1))]
 
-    def load_seek(self, pos):
+    def load_seek(self, pos: int) -> None:
         pass
 
 
 class DXT1Decoder(ImageFile.PyDecoder):
     _pulls_fd = True
 
-    def decode(self, buffer):
+    def decode(self, buffer: bytes) -> tuple[int, int]:
+        assert self.fd is not None
         try:
             self.set_as_raw(_dxt1(self.fd, self.state.xsize, self.state.ysize))
         except struct.error as e:
@@ -266,7 +268,8 @@ def decode(self, buffer):
 class DXT5Decoder(ImageFile.PyDecoder):
     _pulls_fd = True
 
-    def decode(self, buffer):
+    def decode(self, buffer: bytes) -> tuple[int, int]:
+        assert self.fd is not None
         try:
             self.set_as_raw(_dxt5(self.fd, self.state.xsize, self.state.ysize))
         except struct.error as e:
@@ -279,7 +282,7 @@ def decode(self, buffer):
 Image.register_decoder("DXT5", DXT5Decoder)
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] == b"DDS "
 
 
diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
index deae199d50e..2ce8a6c2a11 100644
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -456,8 +456,11 @@ def __setstate__(self, state: list[float | Fraction]) -> None:
         __int__ = _delegate("__int__")
 
 
-def _register_loader(idx: int, size: int):
-    def decorator(func):
+_LoaderFunc = Callable[["ImageFileDirectory_v2", bytes, bool], Any]
+
+
+def _register_loader(idx: int, size: int) -> Callable[[_LoaderFunc], _LoaderFunc]:
+    def decorator(func: _LoaderFunc) -> _LoaderFunc:
         from .TiffTags import TYPES
 
         if func.__name__.startswith("load_"):
@@ -482,12 +485,13 @@ def _register_basic(idx_fmt_name: tuple[int, str, str]) -> None:
     idx, fmt, name = idx_fmt_name
     TYPES[idx] = name
     size = struct.calcsize(f"={fmt}")
-    _load_dispatch[idx] = (  # noqa: F821
-        size,
-        lambda self, data, legacy_api=True: (
-            self._unpack(f"{len(data) // size}{fmt}", data)
-        ),
-    )
+
+    def basic_handler(
+        self: ImageFileDirectory_v2, data: bytes, legacy_api: bool = True
+    ) -> tuple[Any, ...]:
+        return self._unpack(f"{len(data) // size}{fmt}", data)
+
+    _load_dispatch[idx] = size, basic_handler  # noqa: F821
     _write_dispatch[idx] = lambda self, *values: (  # noqa: F821
         b"".join(self._pack(fmt, value) for value in values)
     )
@@ -560,7 +564,7 @@ class ImageFileDirectory_v2(_IFDv2Base):
 
     """
 
-    _load_dispatch: dict[int, Callable[[ImageFileDirectory_v2, bytes, bool], Any]] = {}
+    _load_dispatch: dict[int, tuple[int, _LoaderFunc]] = {}
     _write_dispatch: dict[int, Callable[..., Any]] = {}
 
     def __init__(
@@ -653,10 +657,10 @@ def __getitem__(self, tag):
     def __contains__(self, tag: object) -> bool:
         return tag in self._tags_v2 or tag in self._tagdata
 
-    def __setitem__(self, tag: int, value) -> None:
+    def __setitem__(self, tag: int, value: Any) -> None:
         self._setitem(tag, value, self.legacy_api)
 
-    def _setitem(self, tag: int, value, legacy_api: bool) -> None:
+    def _setitem(self, tag: int, value: Any, legacy_api: bool) -> None:
         basetypes = (Number, bytes, str)
 
         info = TiffTags.lookup(tag, self.group)
@@ -744,10 +748,10 @@ def __delitem__(self, tag: int) -> None:
     def __iter__(self) -> Iterator[int]:
         return iter(set(self._tagdata) | set(self._tags_v2))
 
-    def _unpack(self, fmt: str, data: bytes):
+    def _unpack(self, fmt: str, data: bytes) -> tuple[Any, ...]:
         return struct.unpack(self._endian + fmt, data)
 
-    def _pack(self, fmt: str, *values) -> bytes:
+    def _pack(self, fmt: str, *values: Any) -> bytes:
         return struct.pack(self._endian + fmt, *values)
 
     list(
@@ -824,7 +828,9 @@ def write_undefined(self, value: bytes | int | IFDRational) -> bytes:
         return value
 
     @_register_loader(10, 8)
-    def load_signed_rational(self, data: bytes, legacy_api: bool = True):
+    def load_signed_rational(
+        self, data: bytes, legacy_api: bool = True
+    ) -> tuple[tuple[int, int] | IFDRational, ...]:
         vals = self._unpack(f"{len(data) // 4}l", data)
 
         def combine(a: int, b: int) -> tuple[int, int] | IFDRational:
@@ -1088,7 +1094,7 @@ def __len__(self) -> int:
     def __iter__(self) -> Iterator[int]:
         return iter(set(self._tagdata) | set(self._tags_v1))
 
-    def __setitem__(self, tag: int, value) -> None:
+    def __setitem__(self, tag: int, value: Any) -> None:
         for legacy_api in (False, True):
             self._setitem(tag, value, legacy_api)
 
diff --git a/tox.ini b/tox.ini
index 4b40594550e..70b8bf14584 100644
--- a/tox.ini
+++ b/tox.ini
@@ -36,4 +36,4 @@ deps =
 extras =
     typing
 commands =
-    mypy src Tests {posargs}
+    mypy docs src winbuild Tests {posargs}
diff --git a/winbuild/build_prepare.py b/winbuild/build_prepare.py
index 7129699eb52..1021e4f229f 100644
--- a/winbuild/build_prepare.py
+++ b/winbuild/build_prepare.py
@@ -7,6 +7,7 @@
 import shutil
 import struct
 import subprocess
+from typing import Any
 
 
 def cmd_cd(path: str) -> str:
@@ -43,21 +44,19 @@ def cmd_nmake(
     target: str = "",
     params: list[str] | None = None,
 ) -> str:
-    params = "" if params is None else " ".join(params)
-
     return " ".join(
         [
             "{nmake}",
             "-nologo",
             f'-f "{makefile}"' if makefile is not None else "",
-            f"{params}",
+            f'{" ".join(params)}' if params is not None else "",
             f'"{target}"',
         ]
     )
 
 
 def cmds_cmake(
-    target: str | tuple[str, ...] | list[str], *params, build_dir: str = "."
+    target: str | tuple[str, ...] | list[str], *params: str, build_dir: str = "."
 ) -> list[str]:
     if not isinstance(target, str):
         target = " ".join(target)
@@ -129,7 +128,7 @@ def cmd_msbuild(
 
 
 # dependencies, listed in order of compilation
-DEPS = {
+DEPS: dict[str, dict[str, Any]] = {
     "libjpeg": {
         "url": f"{SF_PROJECTS}/libjpeg-turbo/files/{V['JPEGTURBO']}/"
         f"libjpeg-turbo-{V['JPEGTURBO']}.tar.gz/download",
@@ -538,7 +537,7 @@ def write_script(
             print("    " + line)
 
 
-def get_footer(dep: dict) -> list[str]:
+def get_footer(dep: dict[str, Any]) -> list[str]:
     lines = []
     for out in dep.get("headers", []):
         lines.append(cmd_copy(out, "{inc_dir}"))
@@ -583,6 +582,7 @@ def build_dep(name: str, prefs: dict[str, str], verbose: bool) -> str:
             license_text += f.read()
     if "license_pattern" in dep:
         match = re.search(dep["license_pattern"], license_text, re.DOTALL)
+        assert match is not None
         license_text = "\n".join(match.groups())
     assert len(license_text) > 50
     with open(os.path.join(license_dir, f"{directory}.txt"), "w") as f: