Hibernate3 plugin throws DuplicateMappingException with both hbm.xml and hibernate.cfg.xml

If *.hbm.xml files exists (or are generated) and hibernate.cfg.xml also exists (or are generated) with entries of the *.hbm.xml files, a org.hibernate.DuplicateMappingException gets thrown.

[INFO] ------------------------------------------------------------------------
[INFO] Duplicate class/entity mapping com.foo.Bar
[INFO] ------------------------------------------------------------------------
[INFO] Trace
org.hibernate.DuplicateMappingException: Duplicate class/entity mapping com.foo.Bar
at org.hibernate.cfg.Mappings.addClass(Mappings.java:118)
at org.hibernate.cfg.HbmBinder.bindRoot(HbmBinder.java:154)
at org.hibernate.cfg.Configuration.add(Configuration.java:386)
at org.hibernate.cfg.AnnotationConfiguration.processArtifactsOfType(AnnotationConfiguration.java:261)
at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:210)
at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:997)
at org.codehaus.mojo.hibernate3.HibernateExporterMojo.getConfiguration(HibernateExporterMojo.java:110)
at org.codehaus.mojo.hibernate3.exporter.SchemaExportMojo.doSchemaExport(SchemaExportMojo.java:63)
at org.codehaus.mojo.hibernate3.exporter.Hbm2DDLExporterMojo.doExecute(Hbm2DDLExporterMojo.java:55)
at org.codehaus.mojo.hibernate3.HibernateExporterMojo.execute(HibernateExporterMojo.java:60)
at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:412)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:534)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalWithLifecycle(DefaultLifecycleExecutor.java:475)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:454)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:306)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:273)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:140)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:322)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:115)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:256)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
at org.codehaus.classworlds.Launcher.main(Launcher.java:375)