diff --git a/pytest_parallel/__init__.py b/pytest_parallel/__init__.py
index e584800..ccc7a5a 100644
--- a/pytest_parallel/__init__.py
+++ b/pytest_parallel/__init__.py
@@ -218,7 +218,7 @@ def __init__(self, config):
 
         self.workers = workers
 
-    @pytest.mark.tryfirst
+    @pytest.hookimpl(tryfirst=True)
     def pytest_sessionstart(self, session):
         # make the session threadsafe
         _pytest.runner.SetupState = ThreadLocalSetupState