Can't create empty nt:file under federated parent node

session = repository.login("default");
Node root = session.getRootNode();
Node fed = root.getNode("federation"); <-- Node under federation
Node folder = fed.addNode("Folder" + rnd.nextInt(), "nt:folder");
Node file = fed.addNode("File" + rnd.nextInt(), "nt:file"); 
session.save();

javax.jcr.nodetype.ConstraintViolationException: The values for the '{http://www.jcp.org/jcr/1.0}content' property on node '/federation/File1481898856' no longer satisfy the type and/or constraints on the 'jcr:content' property definition on the 'nt:file' node type definition
          at org.modeshape.jcr.JcrSession$JcrPreSave.process(JcrSession.java:1811)
          at org.modeshape.jcr.cache.document.WritableSessionCache.save(WritableSessionCache.java:501)
          at org.modeshape.jcr.JcrSession.save(JcrSession.java:978)
          at org.modeshape.example.filesystem.ModeShapeExample.main(ModeShapeExample.java:73)
          at org.modeshape.example.embedded.ModeShapeExampleTest.shouldRunApplication(ModeShapeExampleTest.java:35)
          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:601)
          at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
          at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
          at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
          at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
          at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
          at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
          at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
          at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
          at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
          at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
          at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
          at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
          at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
          at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
          at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:76)
          at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:195)
          at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:63)
          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:601)
          at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)