SOAP chokes on Polish characters in page content

I am trying to create a blog entry using SOAP, by invoking this code:

RemoteBlogEntry blog = new RemoteBlogEntry();
blog.setSpace(getSpaceKey());
blog.setTitle(getTitle());
blog.setContent(content);
RemoteBlogEntry result = service.storeBlogEntry(token, blog);

Now, if content happens to have Polish characters in it, like "ą" or "ę", the blog post will be created without content. SOAP docs do not say anything about having to perform any special encodings on strings passed as blog post content.

Have I found a bug?