Running the ant based database configuration tool fails in SOA-P 5.1

Issue

For a new installation of SOA-P 5.1, I am using ant for the database configuration, much like in earlier SOA-P versions.

However, executing ant with a properly configured build.properties yields:

BUG! exception in phase 'parsing' in source unit 'embedded_script_in__opt_jboss_
soa_p_5_jboss_as_tools_schema_build.xml' groovyjarjarantlr.CommonToken cannot be
 cast to groovyjarjarantlr.Token
   at org.codehaus.groovy.control.CompilationUnit.applyToSourceUnits(Compilation
Unit.java:776)
   at org.codehaus.groovy.control.CompilationUnit.compile(CompilationUnit.java:4
38)
   at groovy.lang.GroovyClassLoader.parseClass(GroovyClassLoader.java:277)
   at groovy.lang.GroovyShell.parseClass(GroovyShell.java:572)
   at groovy.lang.GroovyShell.parse(GroovyShell.java:584)
   at groovy.lang.GroovyShell.parse(GroovyShell.java:564)
   at groovy.lang.GroovyShell.parse(GroovyShell.java:611)
   at org.codehaus.groovy.ant.Groovy.execGroovy(Groovy.java:338)
   at org.codehaus.groovy.ant.Groovy.execute(Groovy.java:228)
   at org.apache.tools.ant.UnknownElement.execute(ant-1.6.5.jar.so)

   ...