I have recent texlive. \documentclass[10pt,a4paper,english]{article} \usepackage{ucs} \usepackage[utf8x]{inputenc} \begin{document} What is π \end{document} I get: ! Undefined control sequence. \u-default-960 #1->\textpi l.5 What is π ? ! Emergency stop. \u-default-960 #1->\textpi Any clues?