diff --git a/migen/flow/network.py b/migen/flow/network.py
index 6bf21a004..25d55d1b0 100644
--- a/migen/flow/network.py
+++ b/migen/flow/network.py
@@ -12,7 +12,7 @@ from migen.corelogic.misc import optree
 #      This form is needed to enable actor duplication or sharing during elaboration.
 
 class ActorNode:
-	def __init__(self, actor_class, parameters=None):
+	def __init__(self, actor_class, parameters=dict()):
 		if isinstance(actor_class, type):
 			self.actor_class = actor_class
 			self.parameters = parameters