diff --git a/src/PIL/ImageFile.py b/src/PIL/ImageFile.py
index fce1591ef..69fbafd39 100644
--- a/src/PIL/ImageFile.py
+++ b/src/PIL/ImageFile.py
@@ -34,7 +34,7 @@ import itertools
 import os
 import struct
 import sys
-from typing import IO, TYPE_CHECKING, Any, NamedTuple
+from typing import IO, TYPE_CHECKING, Any, NamedTuple, cast
 
 from . import Image
 from ._deprecate import deprecate
@@ -111,7 +111,7 @@ class ImageFile(Image.Image):
     """Base class for image file format handlers."""
 
     def __init__(
-        self, fp: StrOrBytesPath | IO[bytes] | None = None, filename: str | bytes | None = None
+        self, fp: StrOrBytesPath | IO[bytes], filename: str | bytes | None = None
     ) -> None:
         super().__init__()
 
@@ -134,7 +134,7 @@ class ImageFile(Image.Image):
             self._exclusive_fp = True
         else:
             # stream
-            self.fp = fp
+            self.fp = cast(IO[bytes], fp)
             self.filename = filename if filename is not None else ""
             # can be overridden
             self._exclusive_fp = False
diff --git a/src/PIL/JpegImagePlugin.py b/src/PIL/JpegImagePlugin.py
index 1f54b7e92..e3372a1c2 100644
--- a/src/PIL/JpegImagePlugin.py
+++ b/src/PIL/JpegImagePlugin.py
@@ -848,7 +848,7 @@ def _save_cjpeg(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
 ##
 # Factory for making JPEG and MPO instances
 def jpeg_factory(
-    fp: IO[bytes] | None = None, filename: str | bytes | None = None
+    fp: IO[bytes], filename: str | bytes | None = None
 ) -> JpegImageFile | MpoImageFile:
     im = JpegImageFile(fp, filename)
     try:
diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
index d05c08489..ad898dc8e 100644
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -1126,7 +1126,7 @@ class TiffImageFile(ImageFile.ImageFile):
 
     def __init__(
         self,
-        fp: StrOrBytesPath | IO[bytes] | None = None,
+        fp: StrOrBytesPath | IO[bytes],
         filename: str | bytes | None = None,
     ) -> None:
         self.tag_v2: ImageFileDirectory_v2