Could multiple lines added to the generated code throw this off?

I'm inserting multiple lines at the top of a Webpack bundle for the sake of making this work when I load the bundle in Meteor, like so:

``` js
require("source-map-support/register");
var Npm = Meteor.__mwrContext__.Npm;
var Assets = Meteor.__mwrContext__.Assets;
delete Meteor.__mwrContext__;
var require = Npm.require;

/******/ (function(modules) { // webpackBootstrap
```

The other lines are hacks that allow me to `require` the bundle (Meteor normally loads all server files via `vm.callInThisContext`. I assume that `source-map-support-will` only work if the file is required in as a module like this (if there's another way, let me know).

However one of my users reported the following error https://github.com/jedwards1211/meteor-webpack-react/issues/86:

```
/node_modules/source-map-support/node_modules/source-map/lib/source-map/source-map-consumer.js:281
W20151007-12:26:26.964(-4)? (STDERR) throw new TypeError('Column must be greater than or equal to 0, got '
W20151007-12:26:26.964(-4)? (STDERR) ^
W20151007-12:26:26.964(-4)? (STDERR) TypeError: Column must be greater than or equal to 0, got -23
W20151007-12:26:26.964(-4)? (STDERR) at SourceMapConsumer_findMapping as _findMapping
```

Could this be caused by the extra lines I added to the top of the bundle? I've read some about how source maps work, but I think you would be more prepared to answer this question than me. Thanks!