diff --git a/Tests/test_box_blur.py b/Tests/test_box_blur.py
index d13449044..dfedb48d9 100644
--- a/Tests/test_box_blur.py
+++ b/Tests/test_box_blur.py
@@ -23,11 +23,11 @@ def test_imageops_box_blur() -> None:
     assert isinstance(i, Image.Image)
 
 
-def box_blur(image, radius=1, n=1):
+def box_blur(image, radius: int = 1, n: int = 1):
     return image._new(image.im.box_blur((radius, radius), n))
 
 
-def assert_image(im, data, delta=0) -> None:
+def assert_image(im, data, delta: int = 0) -> None:
     it = iter(im.getdata())
     for data_row in data:
         im_row = [next(it) for _ in range(im.size[0])]
@@ -37,7 +37,7 @@ def assert_image(im, data, delta=0) -> None:
         next(it)
 
 
-def assert_blur(im, radius, data, passes=1, delta=0) -> None:
+def assert_blur(im, radius, data, passes: int = 1, delta: int = 0) -> None:
     # check grayscale image
     assert_image(box_blur(im, radius, passes), data, delta)
     rgba = Image.merge("RGBA", (im, im, im, im))
diff --git a/Tests/test_file_pcx.py b/Tests/test_file_pcx.py
index ea303d4af..38c8514d8 100644
--- a/Tests/test_file_pcx.py
+++ b/Tests/test_file_pcx.py
@@ -87,7 +87,7 @@ def test_large_count(tmp_path) -> None:
     _roundtrip(tmp_path, im)
 
 
-def _test_buffer_overflow(tmp_path, im, size=1024) -> None:
+def _test_buffer_overflow(tmp_path, im, size: int = 1024) -> None:
     _last = ImageFile.MAXBLOCK
     ImageFile.MAXBLOCK = size
     try:
diff --git a/Tests/test_image_reduce.py b/Tests/test_image_reduce.py
index b2bb0c607..3bf2fd1ec 100644
--- a/Tests/test_image_reduce.py
+++ b/Tests/test_image_reduce.py
@@ -126,7 +126,9 @@ def compare_reduce_with_box(im, factor) -> None:
     assert reduced == reference
 
 
-def compare_reduce_with_reference(im, factor, average_diff=0.4, max_diff=1) -> None:
+def compare_reduce_with_reference(
+    im, factor, average_diff=0.4, max_diff: int = 1
+) -> None:
     """Image.reduce() should look very similar to Image.resize(BOX).
 
     A reference image is compiled from a large source area
@@ -171,7 +173,7 @@ def compare_reduce_with_reference(im, factor, average_diff=0.4, max_diff=1) -> N
     assert_compare_images(reduced, reference, average_diff, max_diff)
 
 
-def assert_compare_images(a, b, max_average_diff, max_diff=255) -> None:
+def assert_compare_images(a, b, max_average_diff, max_diff: int = 255) -> None:
     assert a.mode == b.mode, f"got mode {repr(a.mode)}, expected {repr(b.mode)}"
     assert a.size == b.size, f"got size {repr(a.size)}, expected {repr(b.size)}"
 
diff --git a/Tests/test_imagecms.py b/Tests/test_imagecms.py
index b1dcd58a0..7199dd648 100644
--- a/Tests/test_imagecms.py
+++ b/Tests/test_imagecms.py
@@ -334,7 +334,7 @@ def test_extended_information() -> None:
     o = ImageCms.getOpenProfile(SRGB)
     p = o.profile
 
-    def assert_truncated_tuple_equal(tup1, tup2, digits=10) -> None:
+    def assert_truncated_tuple_equal(tup1, tup2, digits: int = 10) -> None:
         # Helper function to reduce precision of tuples of floats
         # recursively and then check equality.
         power = 10**digits
diff --git a/Tests/test_numpy.py b/Tests/test_numpy.py
index f01a63345..6ba95c2d7 100644
--- a/Tests/test_numpy.py
+++ b/Tests/test_numpy.py
@@ -14,7 +14,7 @@ TEST_IMAGE_SIZE = (10, 10)
 
 
 def test_numpy_to_image() -> None:
-    def to_image(dtype, bands=1, boolean=0):
+    def to_image(dtype, bands: int = 1, boolean: int = 0):
         if bands == 1:
             if boolean:
                 data = [0, 255] * 50