Impossible to mock one class with mockito: Receive NoClassDefFoundError

I have around 100 unit test in my Android project. Everything work perfectly. I use JUnit + Mockito + PowerMock (when dealing with difficult static class).

While writing my latest test, I was surprise with this very strange error that I don't understand.

When I do this in the setUp() function:

playerAccessor = mock(PlayerAccessor.class);

All the tests crash with this very strange error:

java.lang.NoClassDefFoundError: android/media/MediaPlayer$OnCompletionListener
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$100(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at org.powermock.core.classloader.MockClassLoader.loadModifiedClass(MockClassLoader.java:178)
    at org.powermock.core.classloader.DeferSupportingClassLoader.loadClass(DeferSupportingClassLoader.java:68)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Unknown Source)
    at java.lang.Class.getDeclaredMethods(Unknown Source)
    at org.mockito.cglib.core.ReflectUtils.addAllMethods(ReflectUtils.java:349)
    at org.mockito.cglib.proxy.Enhancer.getMethods(Enhancer.java:422)
    at org.mockito.cglib.proxy.Enhancer.generateClass(Enhancer.java:457)
    at org.mockito.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
    at org.mockito.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:217)
    at org.mockito.cglib.proxy.Enhancer.createHelper(Enhancer.java:378)
    at org.mockito.cglib.proxy.Enhancer.createClass(Enhancer.java:318)
    at org.mockito.internal.creation.jmock.ClassImposterizer.createProxyClass(ClassImposterizer.java:124)
    at org.mockito.internal.creation.jmock.ClassImposterizer.imposterise(ClassImposterizer.java:60)
    at org.mockito.internal.creation.jmock.ClassImposterizer.imposterise(ClassImposterizer.java:52)
    at org.mockito.internal.creation.CglibMockMaker.createMock(CglibMockMaker.java:24)
    at org.powermock.api.mockito.internal.mockmaker.PowerMockMaker.createMock(PowerMockMaker.java:43)
    at org.mockito.internal.util.MockUtil.createMock(MockUtil.java:32)
    at org.mockito.internal.MockitoCore.mock(MockitoCore.java:59)
    at org.mockito.Mockito.mock(Mockito.java:1258)
    at org.mockito.Mockito.mock(Mockito.java:1135)
    at com.stingray360.clap.ondemand.OnDemandMessageHandlerTest.setUp(OnDemandMessageHandlerTest.java:60)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.junit.internal.runners.MethodRoadie.runBefores(MethodRoadie.java:133)
    at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:96)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:294)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:127)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:282)
    at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)
    at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:207)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:146)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:120)
    at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)
    at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)
    at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:122)
    at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:106)
    at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:53)
    at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: java.lang.ClassNotFoundException: android.media.MediaPlayer$OnCompletionListener
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 62 more

My only clue is that the PlayerAccessor have a function called register which take an object Player which implement the OnCompletionListener interface. But I'm not mocking the Player, I'm mocking the PlayerAccessor.

Do I need to specify something in my mock function so it doesn't try to mock every object used by the PlayerAccessor? Is it something missing from my test (import???).

Thanks!