diff --git a/stdlib/2/collections.pyi b/stdlib/2/collections.pyi
index f61046e1c..3af54ea5b 100644
--- a/stdlib/2/collections.pyi
+++ b/stdlib/2/collections.pyi
@@ -21,6 +21,7 @@ from typing import (
     ValuesView as ValuesView,
 )
 
+_S = TypeVar('_S')
 _T = TypeVar('_T')
 _KT = TypeVar('_KT')
 _VT = TypeVar('_VT')
@@ -53,6 +54,7 @@ class deque(Sized, Iterable[_T], Reversible[_T], Generic[_T]):
     def __setitem__(self, i: int, x: _T) -> None: ...
     def __contains__(self, o: _T) -> bool: ...
     def __reversed__(self) -> Iterator[_T]: ...
+    def __iadd__(self: _S, iterable: Iterable[_T]) -> _S: ...
 
 _CounterT = TypeVar('_CounterT', bound=Counter)
 
diff --git a/stdlib/3/collections/__init__.pyi b/stdlib/3/collections/__init__.pyi
index e1b67e907..87e42cac7 100644
--- a/stdlib/3/collections/__init__.pyi
+++ b/stdlib/3/collections/__init__.pyi
@@ -42,6 +42,7 @@ if sys.version_info >= (3, 5):
         AsyncIterator as AsyncIterator,
     )
 
+_S = TypeVar('_S')
 _T = TypeVar('_T')
 _KT = TypeVar('_KT')
 _VT = TypeVar('_VT')
@@ -235,6 +236,8 @@ class deque(MutableSequence[_T], Generic[_T]):
     def __contains__(self, o: object) -> bool: ...
     def __reversed__(self) -> Iterator[_T]: ...
 
+    def __iadd__(self: _S, iterable: Iterable[_T]) -> _S: ...
+
     if sys.version_info >= (3, 5):
         def __add__(self, other: deque[_T]) -> deque[_T]: ...
         def __mul__(self, other: int) -> deque[_T]: ...