diff --git a/nmigen/fhdl/dsl.py b/nmigen/fhdl/dsl.py
index b193e12..2b14541 100644
--- a/nmigen/fhdl/dsl.py
+++ b/nmigen/fhdl/dsl.py
@@ -38,11 +38,17 @@ class _ModuleBuilderSync(_ModuleBuilderProxy):
     def __getattr__(self, name):
         return _ModuleBuilderSyncCD(self._builder, self._depth, name)
 
+    def __getitem__(self, name):
+        return self.__getattr__(name)
+
     def __setattr__(self, name, value):
         if not isinstance(value, _ModuleBuilderSyncCD):
             raise AttributeError("Cannot assign sync.{} attribute - use += instead"
                                  .format(name))
 
+    def __setitem__(self, name, value):
+        return self.__setattr__(name, value)
+
 
 class _ModuleBuilderRoot:
     def __init__(self, builder, depth):