Shift the offset during eval (using sourcemap)

I'm loading a script from a file, and I'm using eval() to generate a Javascript code like this:

var code = fs.readFileSync('myfile');
var shiftedCode= 'function(param) {' + code + '}\n'+ '//# sourceURL=myfile';
eval(shiftedCode)

The problem is when I put a breakpoint or debugger inside the code, it stops two lines after the correct one because of the added chars at the beginning I suppose.

Is there a way to shift the sourceURL to the correct start point may be using sourcemaps?

Thank you in advance for your help.