ant-assembly-maven-plugin fails with two buildFiles

[ERROR] Failed to execute goal org.nuxeo.build:ant-assembly-maven-plugin:2.0.6-SNAPSHOT:build (packaging) on project nuxeo-distribution-tomcat: Error occurred while running /Users/fguillaume/Eclipse/nuxeo/nuxeo/nuxeo-distribution/nuxeo-distribution-tomcat/src/main/assemble/assembly-cap.xml@0:0
[ERROR] Duplicate target: `'
[ERROR] -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.nuxeo.build:ant-assembly-maven-plugin:2.0.6-SNAPSHOT:build (packaging) on project nuxeo-distribution-tomcat: Error occurred while running /Users/fguillaume/Eclipse/nuxeo/nuxeo/nuxeo-distribution/nuxeo-distribution-tomcat/src/main/assemble/assembly-cap.xml@0:0
Duplicate target: `'
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:216)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:862)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:197)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.MojoExecutionException: Error occurred while running /Users/fguillaume/Eclipse/nuxeo/nuxeo/nuxeo-distribution/nuxeo-distribution-tomcat/src/main/assemble/assembly-cap.xml@0:0
Duplicate target: `'
	at org.nuxeo.build.maven.AntBuildMojo.execute(AntBuildMojo.java:268)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
	... 20 more
Caused by: Duplicate target: `'
	at org.apache.tools.ant.Project.addTarget(Project.java:1123)
	at org.apache.tools.ant.helper.ProjectHelper2$ProjectHandler.onStartElement(ProjectHelper2.java:828)
	at org.apache.tools.ant.helper.ProjectHelper2$RootHandler.startElement(ProjectHelper2.java:574)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:509)
	at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:380)
	at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl$NSContentDriver.scanRootElementHook(XMLNSDocumentScannerImpl.java:614)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:3135)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:880)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
	at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:118)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
	at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
	at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:643)
	at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:281)
	at org.apache.tools.ant.helper.ProjectHelper2.parse(ProjectHelper2.java:178)
	at org.apache.tools.ant.ProjectHelper.configureProject(ProjectHelper.java:93)
	at org.nuxeo.build.ant.AntClient.run(AntClient.java:155)
	at org.nuxeo.build.maven.AntBuildMojo.execute(AntBuildMojo.java:254)
	... 22 more