E.3.1 Unicode Support

In order for Aspell to correctly spell check UTF-8 documents in full screen mode the "wide" version of the curses library must be installed. This is different from the normal version of curses library, and is normally named ‘libcursesw’ (with a ‘w’ at the end) or ‘libncursesw’. UTF-8 documents will not display correctly without the right curses version installed.

In addition your system must also support the mblen function. Although this function was defined in the ISO C89 standard (ANSI X3.159-1989), not all systems have it.