diff --git a/dev/core/src/com/google/gwt/dev/jjs/impl/GwtAstBuilder.java b/dev/core/src/com/google/gwt/dev/jjs/impl/GwtAstBuilder.java
index a2c6575..483275f 100644
--- a/dev/core/src/com/google/gwt/dev/jjs/impl/GwtAstBuilder.java
+++ b/dev/core/src/com/google/gwt/dev/jjs/impl/GwtAstBuilder.java
@@ -2758,7 +2758,7 @@
     }
   }
 
-  public static boolean ENABLED = System.getProperties().containsKey("x.gwt.astBuilder");
+  public static boolean ENABLED = !System.getProperties().containsKey("x.gwt.noAstBuilder");
 
   /**
    * Manually tracked version count.