diff --git a/docs/changelog.md b/docs/changelog.md
index 646afc00..4de319ee 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Use `__protocol_attrs__` for more robust detection of
+  the members of a `Protocol` (#631)
 - Remove more old special cases and improve robustness of
   annotation parsing (#630)
 - Remove dependency on `typing_inspect` (#629)
diff --git a/pyanalyze/checker.py b/pyanalyze/checker.py
index 8c4c3109..f484916a 100644
--- a/pyanalyze/checker.py
+++ b/pyanalyze/checker.py
@@ -432,6 +432,8 @@ def _extract_protocol_members(typ: type) -> Set[str]:
         or is_typing_name(typ, "Protocol")
     ):
         return set()
+    if hasattr(typ, "__protocol_attrs__"):
+        return typ.__protocol_attrs__
     members = set(typ.__dict__) - EXCLUDED_PROTOCOL_MEMBERS
     # Starting in 3.10 __annotations__ always exists on types
     if sys.version_info >= (3, 10) or hasattr(typ, "__annotations__"):