getUsers_with_opportunity__r() is already defined

Getting the following error message when I try to generate enterprise.jar:
/tmp/wsc-scratch8115219967653003368tmp/com/sforce/soap/enterprise/sobject/User.java:4624: getUsers_with_opportunity__r() is already defined in com.sforce.soap.enterprise.sobject.User
public com.sforce.soap.enterprise.QueryResult getUsers_with_opportunity__r() {

Here's the command line I'm using:
java -classpath force-wsc-29.0.0.jar:/usr/local/lib/ST-4.0.8.jar:/usr/local/lib/antlr-4.2-complete.jar com.sforce.ws.tools.wsdlc wsdl.jsp.xml enterprise.jar

Here's my java version:
oliver@ubuntu:~/sfdc$ java -version
openjdk version "1.6.0-internal"
OpenJDK Runtime Environment (build 1.6.0-internal-fredrick_22_oct_2012_10_28-b00)
OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)

Creating metadata.jar works fine.