EnvironmentHelper.changeContext() adds trailing slash?

[Andreas Hartmann]

Hi Cocoon developers,
I just updated to 2.2-dev and got the following error:
The current URI 
(lenya-document-view/authoring/homepage/index/index_en.xml) doesn't 
start with given prefix (lenya-document-/)

Pipeline:
<map:match pattern="lenya-document-*/*/*/**.xml">
  <map:mount uri-prefix="lenya-document-"
             src="{fallback:doctypes.xmap}"
             .../>
</map:match>
The trace led me to EnvironmentHelper.changeContext():
// check for a slash at the beginning to avoid problems with subsitemaps
if ( buffer.charAt(buffer.length()-1) != '/') {
    buffer.append('/');
    this.lastPrefix = this.lastPrefix + '/';
}
I guess this is the code which adds the trailing slash (?)
Is it generally not possible to use a URI prefix for mounting
which does not end with a slash?
Thanks in advance!
-- Andreas