diff --git a/Tests/test_file_gif.py b/Tests/test_file_gif.py
index 75c7019ab..3b60c0860 100644
--- a/Tests/test_file_gif.py
+++ b/Tests/test_file_gif.py
@@ -1171,6 +1171,7 @@ def test_append_images(tmp_path: Path) -> None:
     im.copy().save(out, append_images=ims)
 
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
         assert reread.n_frames == 3
 
     # Tests appending using a generator
diff --git a/Tests/test_file_libtiff.py b/Tests/test_file_libtiff.py
index 40f37430c..ce932f2c7 100644
--- a/Tests/test_file_libtiff.py
+++ b/Tests/test_file_libtiff.py
@@ -1062,8 +1062,8 @@ class TestFileLibTiff(LibTiffTestCase):
             # Set EXIF Orientation to 2
             data = data[:102] + b"\x02" + data[103:]
 
-            with Image.open(io.BytesIO(data)) as im:
-                im = im.transpose(Image.Transpose.FLIP_LEFT_RIGHT)
+            with Image.open(io.BytesIO(data)) as img:
+                im = img.transpose(Image.Transpose.FLIP_LEFT_RIGHT)
             assert_image_equal_tofile(im, "Tests/images/old-style-jpeg-compression.png")
 
     def test_open_missing_samplesperpixel(self) -> None:
diff --git a/Tests/test_file_wmf.py b/Tests/test_file_wmf.py
index 44e213189..dcf5f000f 100644
--- a/Tests/test_file_wmf.py
+++ b/Tests/test_file_wmf.py
@@ -103,10 +103,12 @@ def test_load_set_dpi() -> None:
 
         if not hasattr(Image.core, "drawwmf"):
             return
+        assert isinstance(im, WmfImagePlugin.WmfStubImageFile)
         im.load(im.info["dpi"])
         assert im.size == (1625, 1625)
 
     with Image.open("Tests/images/drawing.emf") as im:
+        assert isinstance(im, WmfImagePlugin.WmfStubImageFile)
         im.load((72, 144))
         assert im.size == (82, 164)