diff --git a/nmigen/compat/genlib/roundrobin.py b/nmigen/compat/genlib/roundrobin.py
index ce88b93..4c9f4a0 100644
--- a/nmigen/compat/genlib/roundrobin.py
+++ b/nmigen/compat/genlib/roundrobin.py
@@ -1,3 +1,6 @@
+import warnings
+
+from ..fhdl.structure import Signal, If, Case
 from ..._utils import deprecated
 from ..fhdl.module import CompatModule