"Duplicate artifact" in LifecycleDependencyResolver

java.lang.IllegalStateException: Duplicate artifact resolution result for project org.eclipse.rcptt:ecl:2.6.0-SNAPSHOT
    at org.apache.maven.project.artifact.DefaultProjectArtifactsCache.assertUniqueKey (DefaultProjectArtifactsCache.java:207)
    at org.apache.maven.project.artifact.DefaultProjectArtifactsCache.put (DefaultProjectArtifactsCache.java:196)
    at org.apache.maven.lifecycle.internal.LifecycleDependencyResolver.resolveProjectDependencies (LifecycleDependencyResolver.java:138)
    at org.apache.maven.lifecycle.internal.MojoExecutor.ensureDependenciesAreResolved (MojoExecutor.java:368)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute (MojoExecutor.java:313)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:212)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:174)
    at org.apache.maven.lifecycle.internal.MojoExecutor.access$000 (MojoExecutor.java:75)
    at org.apache.maven.lifecycle.internal.MojoExecutor$1.run (MojoExecutor.java:162)
    at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute (DefaultMojosExecutionStrategy.java:39)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:159)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:105)
    at io.takari.maven.builder.smart.SmartBuilderImpl.buildProject (SmartBuilderImpl.java:206)
    at io.takari.maven.builder.smart.SmartBuilderImpl$ProjectBuildTask.run (SmartBuilderImpl.java:71)
    at java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:572)
    at java.util.concurrent.FutureTask.run (FutureTask.java:317)
    at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1144)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:642)
    at java.lang.Thread.run (Thread.java:1583)