diff --git a/rhombus/data/private/list_builder.rhm b/rhombus/data/private/list_builder.rhm
index c6eeaf92e..23ba22172 100644
--- a/rhombus/data/private/list_builder.rhm
+++ b/rhombus/data/private/list_builder.rhm
@@ -18,9 +18,11 @@ class ListBuilder():
 
   method add(element):
     storage.add(element)
+    this
 
   method addAll(elements):
     storage.addAll(elements)
+    this
 
   method build():
     match storage.size