diff --git a/build/build.xml b/build/build.xml
index 8774365be..af3ac76ef 100644
--- a/build/build.xml
+++ b/build/build.xml
@@ -76,6 +76,7 @@
             destdir="${compile.dir}"
             includeAntRuntime="no"
             debug="on"
+            source="1.3"
         >
             <src path="${basedir}/source" />
             <classpath>