diff --git a/bsf.spec b/bsf.spec
index c10e6e3..3943053 100644
--- a/bsf.spec
+++ b/bsf.spec
@@ -61,7 +61,7 @@ find -name \*.jar -delete
 
 %build
 export CLASSPATH=$(build-classpath apache-commons-logging xalan-j2)
-ant jar javadocs
+ant -Dsource.level=1.6 jar javadocs
 
 %mvn_artifact %{SOURCE1} build/lib/%{name}.jar