diff --git a/nmigen/compat/fhdl/structure.py b/nmigen/compat/fhdl/structure.py
index 4a99195..1f374d4 100644
--- a/nmigen/compat/fhdl/structure.py
+++ b/nmigen/compat/fhdl/structure.py
@@ -88,6 +88,7 @@ class Case(ast.Switch):
                 raise TypeError("Case object is not a Migen constant")
             if isinstance(k, str) and k == "default":
                 default = v
+                continue
             else:
                 k = k.value
             new_cases.append((k, v))