Problem compiling WidgetSet after a dependency change

Hi,
I am really clueless at this point.
We have a Vaadin 7.6.8 based application. One of the internal maven dependency was changes, a completely internal dependecy that handles api calls to our servers, and now widgetset compilation fails.
The only thing that was change is the replacement of log4j with log4j2 withing that module.
Any ideas?

[INFO]
 --- maven-resources-plugin:2.6:resources (default-resources) @ rotisserie ---
[INFO]
 Using 'UTF-8' encoding to copy filtered resources.
[INFO]
 Copying 7 resources
[INFO]
 
[INFO]
 --- vaadin-maven-plugin:7.6.8:resources (default) @ rotisserie ---
[INFO]
 auto discovered modules [com.watchdox.rotisserie.widgetset.RotisserieWidgetset]

[INFO]
 1 source files from GWT module com.watchdox.rotisserie.widgetset.RotisserieWidgetset
[INFO]
 
[INFO]
 <<< vaadin-maven-plugin:7.6.8:compile (default) < process-resources @ rotisserie <<<
[INFO]
 
[INFO]
 --- vaadin-maven-plugin:7.6.8:compile (default) @ rotisserie ---
[INFO]
 auto discovered modules [com.watchdox.rotisserie.widgetset.RotisserieWidgetset]

[INFO]
 Compiling module com.watchdox.rotisserie.widgetset.RotisserieWidgetset
[INFO]
 [ERROR]
 Unexpected internal compiler error
[INFO]
 java.lang.IllegalArgumentException
[INFO]
 	at org.objectweb.asm.ClassVisitor.<init>(ClassVisitor.java:78)
[INFO]
 	at org.objectweb.asm.ClassVisitor.<init>(ClassVisitor.java:63)
[INFO]
 	at com.google.gwt.dev.javac.BytecodeSignatureMaker$CompileDependencyVisitor.<init>(BytecodeSignatureMaker.java:59)
[INFO]
 	at com.google.gwt.dev.javac.BytecodeSignatureMaker.visitCompileDependenciesInBytecode(BytecodeSignatureMaker.java:227)
[INFO]
 	at com.google.gwt.dev.javac.BytecodeSignatureMaker.getCompileDependencySignature(BytecodeSignatureMaker.java:209)
[INFO]
 	at com.google.gwt.dev.javac.CompiledClass.getSignatureHash(CompiledClass.java:166)
[INFO]
 	at com.google.gwt.dev.javac.Dependencies$Ref.<init>(Dependencies.java:42)
[INFO]
 	at com.google.gwt.dev.javac.Dependencies$Ref.<init>(Dependencies.java:37)
[INFO]
 	at com.google.gwt.dev.javac.Dependencies.resolve(Dependencies.java:114)
[INFO]
 	at com.google.gwt.dev.javac.CompilationStateBuilder$CompileMoreLater.compile(CompilationStateBuilder.java:366)
[INFO]
 	at com.google.gwt.dev.javac.CompilationStateBuilder.doBuildFrom(CompilationStateBuilder.java:580)
[INFO]
 	at com.google.gwt.dev.javac.CompilationStateBuilder.buildFrom(CompilationStateBuilder.java:513)
[INFO]
 	at com.google.gwt.dev.javac.CompilationStateBuilder.buildFrom(CompilationStateBuilder.java:499)
[INFO]
 	at com.google.gwt.dev.cfg.ModuleDef.getCompilationState(ModuleDef.java:668)
[INFO]
 	at com.google.gwt.dev.Precompile.precompile(Precompile.java:255)
[INFO]
 	at com.google.gwt.dev.Precompile.precompile(Precompile.java:229)
[INFO]
 	at com.google.gwt.dev.Precompile.precompile(Precompile.java:145)
[INFO]
 	at com.google.gwt.dev.Compiler.run(Compiler.java:206)
[INFO]
 	at com.google.gwt.dev.Compiler.run(Compiler.java:158)
[INFO]
 	at com.google.gwt.dev.Compiler$1.run(Compiler.java:120)
[INFO]
 	at com.google.gwt.dev.CompileTaskRunner.doRun(CompileTaskRunner.java:55)
[INFO]
 	at com.google.gwt.dev.CompileTaskRunner.runWithAppropriateLogger(CompileTaskRunner.java:50)
[INFO]
 	at com.google.gwt.dev.Compiler.main(Compiler.java:127)