diff --git a/importlib_metadata/_meta.py b/importlib_metadata/_meta.py
index 0c20eff3..219b2a86 100644
--- a/importlib_metadata/_meta.py
+++ b/importlib_metadata/_meta.py
@@ -54,11 +54,11 @@ class SimplePath(Protocol):
     """
 
     def joinpath(
-        self, other: str | os.PathLike[str]
+        self, other: str | os.PathLike[str], /
     ) -> SimplePath: ...  # pragma: no cover
 
     def __truediv__(
-        self, other: str | os.PathLike[str]
+        self, other: str | os.PathLike[str], /
     ) -> SimplePath: ...  # pragma: no cover
 
     @property
diff --git a/newsfragments/542.bugfix.rst b/newsfragments/542.bugfix.rst
new file mode 100644
index 00000000..316e28ba
--- /dev/null
+++ b/newsfragments/542.bugfix.rst
@@ -0,0 +1 @@
+Marked the ``other`` parameter of ``SimplePath.joinpath`` and ``SimplePath.__truediv__`` positional-only, so ``pathlib.Path`` satisfies the protocol under type checkers that compare parameter names.