This problem occurs with the Groovy-1.1-beta-3-SNAPSHOT that comes with Grails 0.6. When I use reflection to query the parameter annotations of a class's method, a call to 'value()' on any of those annotations causes a java.lang.annotation.IncompleteAnnotationException. Note that this does not happen with annotations declared on a method. The attached zip file contains a library and a Groovy script. Simply run the script with the library in the classpath and you should see the error (unless it's been fixed already ).