diff --git a/stdlib/2.7/traceback.pyi b/stdlib/2.7/traceback.pyi
index 4101c207f..291821842 100644
--- a/stdlib/2.7/traceback.pyi
+++ b/stdlib/2.7/traceback.pyi
@@ -13,7 +13,7 @@ def extract_tb(f: TracebackType, limit: int = ...) -> ExtractTbResult: ...
 def extract_stack(f: FrameType = ..., limit: int = ...) -> ExtractTbResult: ...
 def format_list(list: ExtractTbResult) -> List[str]: ...
 def format_exception_only(type: type, value: List[str]) -> str: ...
-def format_exception(type: type, value: List[str], tb: TracebackType, limit: int = ...) -> str: ...
+def format_exception(type: type, value: BaseException, tb: TracebackType, limit: int = ...) -> str: ...
 def format_tb(f: TracebackType, limit: int = ...) -> List[str]: ...
 def format_stack(f: FrameType = ..., limit: int = ...) -> List[str]: ...
 def tb_lineno(tb: TracebackType) -> AnyStr: ...
diff --git a/stdlib/3/traceback.pyi b/stdlib/3/traceback.pyi
index 9d4d2fd9b..77982ed7c 100644
--- a/stdlib/3/traceback.pyi
+++ b/stdlib/3/traceback.pyi
@@ -6,7 +6,7 @@ import typing
 
 # TODO signatures
 def format_exception_only(etype, value): ...
-def format_exception(type: type, value: List[str], tb: TracebackType, limit: int, chain: bool) -> str: ...
+def format_exception(type: type, value: BaseException, tb: TracebackType, limit: int, chain: bool) -> str: ...
 def format_tb(traceback): ...
 def print_exc(limit=..., file=..., chain=...): ...
 def format_exc(limit: int = ..., chain: bool = ...) -> str: ...