diff --git a/stdlib/2.7/traceback.pyi b/stdlib/2.7/traceback.pyi
index 291821842..16120d7ec 100644
--- a/stdlib/2.7/traceback.pyi
+++ b/stdlib/2.7/traceback.pyi
@@ -12,8 +12,8 @@ def print_stack(f: FrameType = ..., limit: int = ..., file: IO[AnyStr] = ...) ->
 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: BaseException, tb: TracebackType, limit: int = ...) -> str: ...
+def format_exception_only(type: type, value: List[str]) -> List[str]: ...
+def format_exception(type: type, value: BaseException, tb: TracebackType, limit: int = ...) -> List[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 77982ed7c..d556ec1e7 100644
--- a/stdlib/3/traceback.pyi
+++ b/stdlib/3/traceback.pyi
@@ -5,8 +5,8 @@ from types import TracebackType
 import typing
 
 # TODO signatures
-def format_exception_only(etype, value): ...
-def format_exception(type: type, value: BaseException, tb: TracebackType, limit: int, chain: bool) -> str: ...
+def format_exception_only(etype, value) -> List[str]: ...
+def format_exception(type: type, value: BaseException, tb: TracebackType, limit: int, chain: bool) -> List[str]: ...
 def format_tb(traceback): ...
 def print_exc(limit=..., file=..., chain=...): ...
 def format_exc(limit: int = ..., chain: bool = ...) -> str: ...