diff --git a/build.xml b/build.xml
index 99b94c7c4..c2c025f3c 100644
--- a/build.xml
+++ b/build.xml
@@ -231,6 +231,7 @@
       </classpath>
       <arg value="-AS3"/>
       <arg value="-strict"/>
+      <arg value="-d"/>
       <arg value="-import"/>
       <arg value="lib/builtin.abc"/>
       <arg value="-import"/>