tycho compiler-plugin cannot compile

When building an OSGI bundle with tycho, the compiler-plugin throws the following error:

   ...AnswerServlet.java:[307]    resp.setCharacterEncoding("UTF-8")    ^^^^^^^^^^^^^^^^^^^^^^^^The method setCharacterEncoding(String) is undefined for the type HTTPServletResponse

As you can see, the Class HTTPServletResponse can be resolved from the build path (the package javax.servlet) successfully, but the Class seems not to have the function setCharacterEncoding(...).

Invesitgations showed, that this method is only included of javax.servlet 2.4+.

However, i am using version 3. There is no other version of this library on my entire file system...so how is that possible?

Building in a standalone java file against this lib/Class/function also works well. Only the tycho compiler plugins fails.

Moreover, i activated the debug-log where the compiler-plugin lists all the build-path. The only entry about javax.servlet was corret.

~\.m2\repository\p2\osgi\bundle\javax.servlet\3.0.0.v201112011016\javax.servlet-3.0.0.v201112011016.jar[+javax/servlet/*;+javax/servlet/http/*;+javax/servlet/annotation/*;+javax/servlet/descriptor/*;+javax/servlet/resources/*;?**/*]

Moreover, there were no other relations to any other javax.servletthings.