diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2c2f74f..df3f44a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 - Adapt test cases to pytest-asyncio 1.0 compatibility https://github.com/python-backoff/backoff/pull/1 from @pastalian
 - Include tests in source distribution https://github.com/python-backoff/backoff/pull/13
 - Added `logging.LoggerAdapter` to `_MaybeLogger` union https://github.com/python-backoff/backoff/pull/34 from @jcbertin
+- Add `exception` to the typing-only `Details` dictionary for cases when `on_exception` is used https://github.com/python-backoff/backoff/pull/35
 
 ### Packaging
 
diff --git a/backoff/_typing.py b/backoff/_typing.py
index 3f61caa..a72960a 100644
--- a/backoff/_typing.py
+++ b/backoff/_typing.py
@@ -27,6 +27,7 @@ class _Details(TypedDict):
 class Details(_Details, total=False):
     wait: float  # present in the on_backoff handler case for either decorator
     value: Any  # present in the on_predicate decorator case
+    exception: Exception  # present in the on_exception decorator case
 
 
 T = TypeVar("T")