Syntax error in nodejs beacuse of +

Suddenly I got in one app a syntax error

SyntaxError: Unexpected token ILLEGAL

that points to this code:

var runtime = require('./');

module.exports = wrap;
function wrap(template, templateName) {
  templateName = templateName || 'template';
  return Function('pug',
    template + '\n' +
    'return ' + templateName + ';'
  )(runtime);
}

The problem is the last +. But when I replace it by a string, the system complains about the + before that one. Its running on a CentOs 6, it worked before and suddenly I get this error messages that cant even be removed by complete reinstalling the app

via Asara