eclcc missing error

The following ECL reports an error when submitted, but not when checked locally:

 
myString := 'Test';
OUTPUT(myString[1.2]);

CLI Used:  
C:\Program Files\HPCCSystems\8.6.30\clienttools\bin\eclcc.exe -syntax -M d:\Users\gordon\git\vscode-ecl\ecl-sample\tmp.ecl