IcedTea Web LinkageError duplicate class definition

Issue

Getting the following error trying to dynamically load classes:

ERROR [com.example.Class1] (AWT-EventQueue-1) [-] [] Command (loader (instance of  net/sourceforge/jnlp/runtime/JNLPClassLoader): attempted  duplicate class definition for name: "com/example/Class2") failed to complete (command phase = FAILED). java.lang.LinkageError: loader (instance of  net/sourceforge/jnlp/runtime/JNLPClassLoader): attempted  duplicate class definition for name: "com/example/Class2"
    at java.lang.ClassLoader.defineClass1(Native Method)
    ... suppressed 8 lines
    at net.sourceforge.jnlp.runtime.JNLPClassLoader.access$1701(JNLPClassLoader.java:105)
    at net.sourceforge.jnlp.runtime.JNLPClassLoader$5.run(JNLPClassLoader.java:1752)
    at net.sourceforge.jnlp.runtime.JNLPClassLoader$5.run(JNLPClassLoader.java:1749)
    ...
    at net.sourceforge.jnlp.runtime.JNLPClassLoader.findClass(JNLPClassLoader.java:1748)
    at net.sourceforge.jnlp.runtime.JNLPClassLoader.loadClassExt(JNLPClassLoader.java:1785)
    at net.sourceforge.jnlp.runtime.JNLPClassLoader.loadClass(JNLPClassLoader.java:1585)
    at com.calypso.tk.infosec.rt.DefaultRuntimeAccessor.loadClass(DefaultRuntimeAccessor.java:231)
    at com.exmple.Class3.doSomething(Class3.java:100)
...