The \suppressmathparerror=1 should suppress \par errors in math mode. OK, this works: ----------------- \suppressmathparerror=1 $$ a b $$ \bye ------------------ but the following example gives error: Display math should end with \Ustopdisplaymath ------------------- \suppressmathparerror=1 $$ \halign{#\cr a\cr} $$ \bye ------------------- The LuaTeX manual does not exactly describes the behavior of this case. So, I don't know if this is feature or bug. Note that the second example is primitive meaning of something like this: -------------------- $$ \eqalignno{...} $$ -------------------- If a user know that "empty lines are allowed in math mode" then he/she could leave empty line after \eqalignno too. Best regards Petr Olsak