Hi, Sorry to be a pain: %% $ luatex --fmt luatex-plain tst01.tex This is LuaTeX, Version beta-0.79.1 (TeX Live 2014/dev) (rev 4972) (format=luatex-plain 2014.5.7) 7 MAY 2014 11:48 \write18 enabled. **tst01.tex 8<.... (../tex/generic/context/luatex/luatex mplib.tex) ! Missing { inserted. <to be read again> $ l.2 Inline $\sqrt{1.2}$ math. %-- same for $\root n of x$ Works fine with `luatex` and `pdftex` from MacTeXbasic 2013 (+extras) LuaTeX, Version beta-0.76.0-2013061817 (TeX Live 2013) (rev 4627) pdfTeX 3.1415926-2.5-1.40.14 (TeX Live 2013) Font issue with roots?