diff --git a/src/griffe/diff.py b/src/griffe/diff.py
index 7521f901..b36617de 100644
--- a/src/griffe/diff.py
+++ b/src/griffe/diff.py
@@ -415,7 +415,10 @@ def _attribute_incompatibilities(old_attribute: Attribute, new_attribute: Attrib
     # if old_attribute.annotation is not None and new_attribute.annotation is not None:
     #     if not is_subhint(new_attribute.annotation, old_attribute.annotation):
     if old_attribute.value != new_attribute.value:
-        yield AttributeChangedValueBreakage(new_attribute, old_attribute.value, new_attribute.value)
+        if new_attribute.value is None:
+            yield AttributeChangedValueBreakage(new_attribute, old_attribute.value, "unset")
+        else:
+            yield AttributeChangedValueBreakage(new_attribute, old_attribute.value, new_attribute.value)
 
 
 def _alias_incompatibilities(
diff --git a/tests/test_diff.py b/tests/test_diff.py
index 4d1f675f..c1663a31 100644
--- a/tests/test_diff.py
+++ b/tests/test_diff.py
@@ -154,6 +154,11 @@
             "def a(x): ...",
             [BreakageKind.PARAMETER_REMOVED],
         ),
+        (
+            "class a:\n\tb: int | None = None",
+            "class a:\n\tb: int",
+            [BreakageKind.ATTRIBUTE_CHANGED_VALUE],
+        ),
         (
             "def a() -> int: ...",
             "def a() -> str: ...",