diff --git a/pyi.py b/pyi.py
index 27415850..25c41553 100644
--- a/pyi.py
+++ b/pyi.py
@@ -2020,7 +2020,7 @@ def _check_class_method_for_bad_typevars(
             self._Y019_error(method, cls_typevar)
 
     def check_self_typevars(self, node: ast.FunctionDef | ast.AsyncFunctionDef) -> None:
-        pos_or_keyword_args = node.args.args
+        pos_or_keyword_args = node.args.posonlyargs + node.args.args
 
         if not pos_or_keyword_args:
             return
diff --git a/tests/typevar.pyi b/tests/typevar.pyi
index bda9876d..a8012889 100644
--- a/tests/typevar.pyi
+++ b/tests/typevar.pyi
@@ -42,6 +42,7 @@ class GoodClass:
     def __new__(cls: type[Self], *args: list[int], **kwargs: set[str]) -> Self: ...
     def good_instance_method_1(self: Self, arg: bytes) -> Self: ...
     def good_instance_method_2(self, arg1: _S2, arg2: _S2) -> _S2: ...
+    def good_instance_method_3(self, arg1: _S2, /, arg2: _S2) -> _S2: ...
     @classmethod
     def good_cls_method_1(cls: type[Self], arg: int) -> Self: ...
     @classmethod