diff --git a/build.xml b/build.xml
index 9377409c4..cfb6cc966 100644
--- a/build.xml
+++ b/build.xml
@@ -122,7 +122,9 @@
  </target>
 
  <target name="phpunit" description="Run unit tests with PHPUnit">
-  <exec executable="phpunit" failonerror="false"/>
+  <exec executable="phpunit">
+    <arg path="${basedir}/workflow/engine/src" />
+  </exec>
  </target>
 
  <target name="phpcb" description="Aggregate tool output with PHP_CodeBrowser">