Package titlesec Error: Unknown shape

I am trying to modify the basic article class section headers so that the main section level is centered and has the format “1. XXXXX “. To accomplish this I am trying to use the titlesec package. However when I specify the titelformat I get the following error:

Package titlesec Error: Unknown shape.

Even a minimum working example that I found and tweaked from here won’t work. What I specifically tried compiling using pdflatex was

documentclass[11pt]{article}

usepackage{titlesec}
titleformat{section}[block]
  {fontsize{12}{15}bfseriessffamilyfilecenter}
  {thesection}
  {1em}
  {MakeUppercase}

begin{document}

thesection{Behold}
Blah blah blah.  Something about something important, maybe.

end{document}

Is there an issue with my LaTeX distribution or has something changed since this example was made and now? Thanks!