diff --git a/src/__init__.py b/src/__init__.py
index 8917831..f0f62b9 100644
--- a/src/mpi4py/__init__.py
+++ b/src/mpi4py/__init__.py
@@ -102,7 +102,7 @@ def rc(**kargs): # pylint: disable=invalid-name
rc.initialize = True
rc.threads = True
-rc.thread_level = 'multiple'
+rc.thread_level = 'serialized'
rc.finalize = None
rc.fast_reduce = True
rc.recv_mprobe = True