python
diff --git a/Collapse file
‎mypy/stubtest.py‎
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+11-2Lines changed: 11 additions & 2 deletions b/Collapse file
‎mypy/stubtest.py‎
Copy file name to clipboardExpand all lines: mypy/stubtest.py
+11-2Lines changed: 11 additions & 2 deletions
diff --git a/Collapse file
‎mypy/test/teststubtest.py‎
Copy file name to clipboardExpand all lines: mypy/test/teststubtest.py
+5-4Lines changed: 5 additions & 4 deletions b/Collapse file
‎mypy/test/teststubtest.py‎
Copy file name to clipboardExpand all lines: mypy/test/teststubtest.py
+5-4Lines changed: 5 additions & 4 deletions
@@ -1898,8 +1898,17 @@ def is_expected_dunder(name: str, *, stub: nodes.TypeInfo, existing_stub_names:
     if name == "__ge__" and {"__gt__", "__eq__"}.issubset(existing_stub_names):
         return True
 
-    return (name in ("__or__", "__ror__", "__ior__") and stub.has_base("typing.Mapping")) or (
-        name in ("__mul__", "__rmul__", "__imul__") and stub.has_base("typing.Sequence")
+    if (name in ("__or__", "__ror__") and stub.has_base("typing.Mapping")) or (
+        name in ("__mul__", "__rmul__") and stub.has_base("typing.Sequence")
+    ):
+        return True
+
+    # In-place syntax such as `*=` and `|=` can work with immutable types (for example,
+    # tuples or frozensets), but generally delegates to the non-in-place dunder in
+    # these cases. The in-place dunders themselves are generally only defined for
+    # mutable types.
+    return (name == "__ior__" and stub.has_base("typing.MutableMapping")) or (
+        name == "__imul__" and stub.has_base("typing.MutableSequence")
     )
 
 
 
@@ -81,6 +81,7 @@ class Coroutine(Generic[_T_co, _S, _R]): ...
 class Iterable(Generic[_T_co]): ...
 class Iterator(Iterable[_T_co]): ...
 class Mapping(Generic[_K, _V]): ...
+class MutableMapping(Mapping[_K, _V]): ...
 class Match(Generic[AnyStr]): ...
 class Sequence(Iterable[_T_co]): ...
 class Tuple(Sequence[_T_co]): ...
@@ -1981,14 +1982,14 @@ class MappingOr:
         )
         yield Case(
             stub="""
-            from typing import Mapping
-            class MappingIor(Mapping[str, int]): ...
+            from typing import MutableMapping
+            class MutableMappingIor(MutableMapping[str, int]): ...
             """,
             runtime="""
-            class MappingIor:
+            class MutableMappingIor:
                 __ior__ = dict.__ior__
             """,
-            error="MappingIor.__ior__",
+            error="MutableMappingIor.__ior__",
         )
         yield Case(
             stub="""