diff -r 572668ef742b -r e3c851a14f16 src/Zone.cpp
--- a/src/Zone.cpp	Tue Dec 25 17:02:07 2012 -0800
+++ b/src/Zone.cpp	Tue Dec 25 18:13:02 2012 -0800
@@ -180,6 +180,13 @@
     stack_.accept(visitor);
 }
 
+void
+Zone::sweepWeakRoots()
+{
+    symbols_->sweep();
+    types()->sweep();
+}
+
 String *
 Zone::makeSymbol(const char *str, size_t length)
 {