NPE in yangtools when parsing yang file

Here is the exeception:

[ERROR] yang-to-sources: Unable to parse yang files from /Users/hagbard/try/controller/opendaylight/md-sal/model/model-flow-base/src/main/yang
java.lang.NullPointerException
at org.opendaylight.yangtools.yang.parser.builder.impl.CopyUtils.getdata(CopyUtils.java:478)
at org.opendaylight.yangtools.yang.parser.builder.impl.CopyUtils.copy(CopyUtils.java:332)
at org.opendaylight.yangtools.yang.parser.builder.impl.CopyUtils.copy(CopyUtils.java:345)
at org.opendaylight.yangtools.yang.parser.builder.impl.CopyUtils.copy(CopyUtils.java:212)
at org.opendaylight.yangtools.yang.parser.builder.impl.CopyUtils.copy(CopyUtils.java:51)
at org.opendaylight.yangtools.yang.parser.builder.impl.GroupingBuilderImpl.instantiateChildNodes(GroupingBuilderImpl.java:71)
at org.opendaylight.yangtools.yang.parser.impl.YangParserImpl.resolveUses(YangParserImpl.java:1116)
at org.opendaylight.yangtools.yang.parser.impl.YangParserImpl.resolveUsesForGroupings(YangParserImpl.java:1076)
at org.opendaylight.yangtools.yang.parser.impl.YangParserImpl.build(YangParserImpl.java:667)
at org.opendaylight.yangtools.yang.parser.impl.YangParserImpl.parseYangModelSources(YangParserImpl.java:359)
at org.opendaylight.yangtools.yang.parser.impl.YangParserImpl.parseYangModelsFromStreamsMapped(YangParserImpl.java:313)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.processYang(YangToSourcesProcessor.java:151)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.execute(YangToSourcesProcessor.java:82)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesMojo.execute(YangToSourcesMojo.java:122)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
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:84)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)