Hi, I have read http://thread.gmane.org/gmane.comp.tex.context/3540, but why does the following \appendtoks \let\#\hashletter \to \everyMPgraphic \startuseMPgraphic{foo} vardef foo@\#(expr x) = enddef; \stopuseMPgraphic \startuseMPgraphic{goo} \includeMPgraphic{foo} foo.foo(1); \stopuseMPgraphic \starttext \useMPgraphic{goo} \stoptext gives the error: ! Undefined control sequence. <argument> vardef foo@\# (expr x) = enddef; \handleuseMPgraphic #1#2#3->#3 <argument> \includeMPgraphic {foo} foo.foo(1); \writecheckedMPgraphic ...icfalse \edef \ascii {#1 }\convertcommand \ascii \t... \startMPgraphic ...hic \writecheckedMPgraphic {#1} \stopwritingMPgraphic \handleuseMPgraphic ...MPgraphic #3\stopMPgraphic \ifMPrun \else \loadMPgrap... ... Nicola