diff --git a/migen/sim/generic.py b/migen/sim/generic.py
index 178366128..b553dc7b5 100644
--- a/migen/sim/generic.py
+++ b/migen/sim/generic.py
@@ -76,6 +76,8 @@ end
 
 class Simulator:
 	def __init__(self, fragment, top_level=None, sim_runner=None, sockaddr="simsocket", **vopts):
+		if not isinstance(fragment, Fragment):
+			fragment = fragment.get_fragment()
 		if top_level is None:
 			top_level = TopLevel()
 		if sim_runner is None: