diff --git a/ant.spec b/ant.spec
index 847cf69..c56b68f 100644
--- a/ant.spec
+++ b/ant.spec
@@ -341,6 +341,10 @@ export CLASSPATH=$(%{_bindir}/build-classpath jaxp_parser_impl xml-commons-apis 
 [ -z "$JAVA_HOME" ] && JAVA_HOME=%{_jvmdir}/java
 export JAVA_HOME
 sh build.sh --noconfig jars javadocs
+if [ ! -f build/lib/%{name}.jar ]; then
+    jcf-dump 'build/classes/org/apache/tools/ant/IntrospectionHelper$1.class'
+    exit 1
+fi
 
 # -----------------------------------------------------------------------------