error: custom classloader succeeds with run, fails with test after upgrading from sbt 0.12.2 to sbt 0.13.7-M4

gistfile1.txt

> test
java.lang.reflect.InvocationTargetException
	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 com.julianpeeters.caseclass.generator.DynamicClassLoader.loadClass(DynamicClassLoader.java:19)
	at com.julianpeeters.caseclass.generator.DynamicCaseClass.<init>(DynamicCaseClass.scala:24)
	at IntIntSpec.<init>(IntIntSpec.scala:17)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at org.specs2.reflect.Classes$class.createInstanceFor(Classes.scala:157)
	at org.specs2.reflect.Classes$.createInstanceFor(Classes.scala:213)
	at org.specs2.reflect.Classes$$anonfun$createInstanceOfEither$1.apply(Classes.scala:147)
	at org.specs2.reflect.Classes$$anonfun$createInstanceOfEither$1.apply(Classes.scala:147)
	at scala.Option.map(Option.scala:145)
	at org.specs2.reflect.Classes$class.createInstanceOfEither(Classes.scala:147)
	at org.specs2.reflect.Classes$.createInstanceOfEither(Classes.scala:213)
	at org.specs2.reflect.Classes$class.org$specs2$reflect$Classes$$createInstanceForConstructor(Classes.scala:120)
	at org.specs2.reflect.Classes$$anonfun$5.apply(Classes.scala:98)
	at org.specs2.reflect.Classes$$anonfun$5.apply(Classes.scala:98)
	at scala.collection.GenSeqViewLike$Mapped$class.apply(GenSeqViewLike.scala:48)
	at scala.collection.SeqViewLike$$anon$3.apply(SeqViewLike.scala:78)
	at scala.collection.GenSeqViewLike$Filtered$class.index(GenSeqViewLike.scala:83)
	at scala.collection.SeqViewLike$$anon$5.index$lzycompute(SeqViewLike.scala:80)
	at scala.collection.SeqViewLike$$anon$5.index(SeqViewLike.scala:80)
	at scala.collection.GenSeqViewLike$Filtered$class.apply(GenSeqViewLike.scala:91)
	at scala.collection.SeqViewLike$$anon$5.apply(SeqViewLike.scala:80)
	at scala.collection.GenSeqViewLike$Mapped$class.apply(GenSeqViewLike.scala:48)
	at scala.collection.SeqViewLike$$anon$3.apply(SeqViewLike.scala:78)
	at org.specs2.reflect.Classes$class.tryToCreateObjectEither(Classes.scala:103)
	at org.specs2.reflect.Classes$.tryToCreateObjectEither(Classes.scala:213)
	at org.specs2.reflect.Classes$class.tryToCreateObject(Classes.scala:70)
	at org.specs2.reflect.Classes$.tryToCreateObject(Classes.scala:213)
	at org.specs2.specification.SpecificationStructure$.createSpecificationFromClassOrObject(BaseSpecification.scala:126)
	at org.specs2.specification.SpecificationStructure$.createSpecificationEither(BaseSpecification.scala:117)
	at org.specs2.runner.SbtRunner.org$specs2$runner$SbtRunner$$specificationRun(SbtRunner.scala:70)
	at org.specs2.runner.SbtRunner$$anonfun$newTask$1$$anon$5.execute(SbtRunner.scala:57)
	at sbt.TestRunner.runTest$1(TestFramework.scala:76)
	at sbt.TestRunner.run(TestFramework.scala:85)
	at sbt.TestFramework$$anon$2$$anonfun$$init$$1$$anonfun$apply$8.apply(TestFramework.scala:202)
	at sbt.TestFramework$$anon$2$$anonfun$$init$$1$$anonfun$apply$8.apply(TestFramework.scala:202)
	at sbt.TestFramework$.sbt$TestFramework$$withContextLoader(TestFramework.scala:185)
	at sbt.TestFramework$$anon$2$$anonfun$$init$$1.apply(TestFramework.scala:202)
	at sbt.TestFramework$$anon$2$$anonfun$$init$$1.apply(TestFramework.scala:202)
	at sbt.TestFunction.apply(TestFramework.scala:207)
	at sbt.Tests$$anonfun$9.apply(Tests.scala:216)
	at sbt.Tests$$anonfun$9.apply(Tests.scala:216)
	at sbt.std.Transform$$anon$3$$anonfun$apply$2.apply(System.scala:44)
	at sbt.std.Transform$$anon$3$$anonfun$apply$2.apply(System.scala:44)
	at sbt.std.Transform$$anon$4.work(System.scala:63)
	at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:226)
	at sbt.Execute$$anonfun$submit$1$$anonfun$apply$1.apply(Execute.scala:226)
	at sbt.ErrorHandling$.wideConvert(ErrorHandling.scala:17)
	at sbt.Execute.work(Execute.scala:235)
	at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:226)
	at sbt.Execute$$anonfun$submit$1.apply(Execute.scala:226)
	at sbt.ConcurrentRestrictions$$anon$4$$anonfun$1.apply(ConcurrentRestrictions.scala:159)
	at sbt.CompletionService$$anon$2.call(CompletionService.scala:28)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
	at java.util.concurrent.FutureTask.run(FutureTask.java:166)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
	at java.util.concurrent.FutureTask.run(FutureTask.java:166)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:724)
Caused by: java.lang.LinkageError: loader (instance of  sbt/classpath/ClasspathFilter): attempted  duplicate class definition for name: "models/MyRecord_IntIntSpec"
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:788)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:631)
	... 67 more