diff --git a/tests/hazmat/primitives/test_padding.py b/tests/hazmat/primitives/test_padding.py
index 392ea73..9da8ea7 100644
--- a/tests/hazmat/primitives/test_padding.py
+++ b/tests/hazmat/primitives/test_padding.py
@@ -99,3 +99,51 @@
             unpadder.update(b"")
         with pytest.raises(AlreadyFinalized):
             unpadder.finalize()
+
+
+class TestANSIX923(object):
+    @pytest.mark.parametrize(("size", "unpadded", "padded"), [
+        (
+            128,
+            b"1111111111",
+            b"1111111111\x00\x00\x00\x00\x00\x06",
+        ),
+        (
+            128,
+            b"111111111111111122222222222222",
+            b"111111111111111122222222222222\x00\x02",
+        ),
+        (
+            128,
+            b"1" * 16,
+            b"1" * 16 + b"\x00" * 15 + b"\x10",
+        ),
+        (
+            128,
+            b"1" * 17,
+            b"1" * 17 + b"\x00" * 14 + b"\x0F",
+        )
+    ])
+    def test_pad(self, size, unpadded, padded):
+        padder = padding.ANSIX923(size).padder()
+        result = padder.update(unpadded)
+        result += padder.finalize()
+        assert result == padded
+
+    @pytest.mark.parametrize(("size", "unpadded", "padded"), [
+        (
+            128,
+            b"1111111111",
+            b"1111111111\x00\x00\x00\x00\x00\x06",
+        ),
+        (
+            128,
+            b"111111111111111122222222222222",
+            b"111111111111111122222222222222\x00\x02",
+        ),
+    ])
+    def test_unpad(self, size, unpadded, padded):
+        unpadder = padding.ANSIX923(size).unpadder()
+        result = unpadder.update(padded)
+        result += unpadder.finalize()
+        assert result == unpadded
diff --git a/tests/hypothesis/test_padding.py b/tests/hypothesis/test_padding.py
index 21c9a23..29d726f 100644
--- a/tests/hypothesis/test_padding.py
+++ b/tests/hypothesis/test_padding.py
@@ -5,7 +5,7 @@
 from hypothesis import given
 from hypothesis.strategies import binary, integers
 
-from cryptography.hazmat.primitives.padding import PKCS7
+from cryptography.hazmat.primitives.padding import ANSIX923, PKCS7
 
 
 @given(integers(min_value=1, max_value=31), binary())
@@ -19,3 +19,14 @@
     padded = padder.update(data) + padder.finalize()
 
     assert unpadder.update(padded) + unpadder.finalize() == data
+
+
+@given(integers(min_value=1, max_value=31), binary())
+def test_ansix923(block_size, data):
+    a = ANSIX923(block_size=block_size * 8)
+    padder = a.padder()
+    unpadder = a.unpadder()
+
+    padded = padder.update(data) + padder.finalize()
+
+    assert unpadder.update(padded) + unpadder.finalize() == data