GWT 2.5.0: gwtc failed: java.lang.RuntimeException: Unexpected IOException on in-memory stream

Got following error when compiling a GWT project using GWT 2.5.0:

[INFO]    [ERROR] Unexpected internal compiler error
[INFO] java.lang.RuntimeException: Unexpected IOException on in-memory stream
[INFO]  at com.google.gwt.dev.javac.CompilationUnit.getTypes(CompilationUnit.java:360)

Work around is remove gwt-unitCache folder.