Rules / Build

Missing } inserted — Missing brace

A { group is still open where TeX needs it closed, for example at the end of a formula.

Fix

Close every { before the formula or environment ends.

Example

Reproduced on TeX Live 2026 by CI · pdflatex · corpus/missing-brace-inserted

Group opened in a formula is not closed before the formula ends

Fails: main.tex
\documentclass{article}
\begin{document}
The variance $\sigma^{2$ is small for every run.
\end{document}
Fixed
\documentclass{article}
\begin{document}
The variance $\sigma^{2}$ is small for every run.
\end{document}
What TeX prints in main.log
! Missing } inserted.
<inserted text> 
                }
l.3 The variance $\sigma^{2$
                             is small for every run.
I've inserted something that you may have forgotten.
(See the <inserted text> above.)
With luck, this will get me unwedged. But if you
really didn't forget anything, try typing `2' now; then
my insertion and my current dilemma will both disappear.