Hi, Following MWE produces the error given below. I have been able to include other tikz libraries (arrows, decorations) successfully. *MWE* \usemodule[tikz] \usetikzlibrary{external} \starttext A \stoptext *Error* --------------------------------------------- ! Missing number, treated as zero. system > tex > error on line 1290 in file /home/deven/context/tex/texmf-modules/tex/generic/pgf/frontendlayer/tikz/libraries/tikzexternalshared.code.tex: Missing number, treated as zero ... 1280 \gdef\tikzexternal@activate@normal@dq{\let"=\tikzexternal@normal@dq} 1281 \gdef\tikzexternal@activate@normal@sq{\let'=\tikzexternal@normal@sq} 1282 \gdef\tikzexternal@activate@normal@semic{\let;=\tikzexternal@normal@semic} 1283 \gdef\tikzexternal@activate@normal@and{\let&=\tikzexternal@normal@and} 1284 \gdef\tikzexternal@activate@normal@dash{\let-=\tikzexternal@normal@dash} 1285 \catcode`\|=0 1286 \catcode`\\=12 1287 |xdef|tikzexternal@normal@backslash{\}% 1288 } 1289 { 1290 >> \catcode`\^^I=12 1291 \catcode`\$=12 1292 \catcode`\%=12 1293 \catcode`\#=12 1294 \gdef\tikzexternal@HASHchar{#} 1295 \gdef\tikzexternal@TABchar{^^I}\gdef\tikzexternal@PERCENTchar{%}\xdef\tikzexternal@DOLLARchar{$}} 1296 1297 % Creates the '/tikz/external/system call' command as string and 1298 % returns it into the (global!) macro #2. 1299 % #1: the image file name (as returned by 1300 % \tikzexternalgetnextfilename) <to be read again> ^ l.1290 \catcode`\^^ I=12