diff --git a/Tests/test_file_vtf.py b/Tests/test_file_vtf.py
index 62a6ad47d..6a7032494 100644
--- a/Tests/test_file_vtf.py
+++ b/Tests/test_file_vtf.py
@@ -24,7 +24,7 @@ from .helper import assert_image_equal, assert_image_similar
         (2000, 2048),
     ],
 )
-def test_closest_power(size: int, expected_size: int):
+def test_closest_power(size: int, expected_size: int) -> None:
     assert _closest_power(size) == expected_size
 
 
@@ -42,7 +42,7 @@ def test_closest_power(size: int, expected_size: int):
         ((1024, 1), 11),
     ],
 )
-def test_get_mipmap_count(size: tuple[int, int], expected_count: int):
+def test_get_mipmap_count(size: tuple[int, int], expected_count: int) -> None:
     assert _get_mipmap_count(*size) == expected_count
 
 
@@ -64,7 +64,7 @@ def test_get_mipmap_count(size: tuple[int, int], expected_count: int):
 )
 def test_get_texture_size(
     pixel_format: VtfPF, size: tuple[int, int], expected_size: int
-):
+) -> None:
     assert _get_texture_size(pixel_format, *size) == expected_size
 
 
@@ -82,15 +82,17 @@ def test_get_texture_size(
         ("Tests/images/vtf_rgba8888.png", "Tests/images/vtf_rgba8888.vtf", "RGBA", 0),
     ],
 )
-def test_vtf_read(etalon_path: str, file_path: str, expected_mode: str, epsilon: float):
-    e = Image.open(etalon_path)
-    f = Image.open(file_path)
-    assert f.mode == expected_mode
-    e = e.convert(expected_mode)
-    if epsilon == 0:
-        assert_image_equal(e, f)
-    else:
-        assert_image_similar(e, f, epsilon)
+def test_vtf_read(
+    etalon_path: str, file_path: str, expected_mode: str, epsilon: float
+) -> None:
+    with Image.open(file_path) as f:
+        assert f.mode == expected_mode
+        with Image.open(etalon_path) as e:
+            converted_e = e.convert(expected_mode)
+        if epsilon == 0:
+            assert_image_equal(converted_e, f)
+        else:
+            assert_image_similar(converted_e, f, epsilon)
 
 
 @pytest.mark.parametrize(
@@ -109,7 +111,7 @@ def test_vtf_read(etalon_path: str, file_path: str, expected_mode: str, epsilon:
 )
 def test_vtf_save(
     pixel_format: VtfPF, file_path: str, expected_mode: str, epsilon: float, tmp_path
-):
+) -> None:
     f: Image.Image = Image.open(file_path)
     out = (tmp_path / "tmp.vtf").as_posix()
     f.save(out, pixel_format=pixel_format)
diff --git a/src/PIL/VtfImagePlugin.py b/src/PIL/VtfImagePlugin.py
index 8aa9c4324..7e123cdae 100644
--- a/src/PIL/VtfImagePlugin.py
+++ b/src/PIL/VtfImagePlugin.py
@@ -14,9 +14,9 @@ from __future__ import annotations
 
 import struct
 from enum import IntEnum, IntFlag
-from io import BufferedIOBase, BytesIO
+from io import BytesIO
 from math import ceil, log
-from typing import NamedTuple
+from typing import IO, NamedTuple
 
 from . import Image, ImageFile
 
@@ -149,7 +149,7 @@ def _get_texture_size(pixel_format: VtfPF, width, height):
     raise VTFException(msg)
 
 
-def _get_mipmap_count(width: int, height: int):
+def _get_mipmap_count(width: int, height: int) -> int:
     mip_count = 1
     while True:
         mip_width = width >> mip_count
@@ -159,8 +159,9 @@ def _get_mipmap_count(width: int, height: int):
         mip_count += 1
 
 
-def _write_image(fp: BufferedIOBase, im: Image.Image, pixel_format: VtfPF):
+def _write_image(fp: IO[bytes], im: Image.Image, pixel_format: VtfPF) -> None:
     extents = (0, 0) + im.size
+    encoder_args: tuple[int, str] | tuple[str, int, int]
     if pixel_format == VtfPF.DXT1:
         encoder = "bcn"
         encoder_args = (1, "DXT1")
@@ -309,8 +310,7 @@ class VtfImageFile(ImageFile.ImageFile):
         self.tile = [tile]
 
 
-def _save(im, fp, filename):
-    im: Image.Image
+def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
     if im.mode not in ("RGB", "RGBA", "L", "LA"):
         msg = f"cannot write mode {im.mode} as VTF"
         raise OSError(msg)
@@ -406,7 +406,7 @@ def _save(im, fp, filename):
     _write_image(fp, im, pixel_format)
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     valid_header = prefix[:4] == b"VTF\x00"
     valid_version = struct.unpack_from("<2I", prefix, 4) >= (7, 0)
     return valid_header and valid_version