Ambigious reference for ExtensionAttribute when using Iron Python in Asp.Net

I get the following error when starting an Asp.Net site that uses an assembly that in turn makes use of the dlr and Iron Python for scripting.

BC30560: 'ExtensionAttribute' is ambiguous in the namespace 'System.Runtime.CompilerServices'.

The issue seems to be known and there's a workaround in the issue tracker.

However it says that they...

... hope that this workaround will not be necessary in the next release.

The latest release (the one that I'm using) is a later release than the one mentioned in the report. I've also tried downloading the file supplied in the issue tracker and replace the one from the current release, but that does not work either.

Is there a solution to this other than downloading the source and doing the build manually?

The bug only seems to have been closed because of the DLLs attached to the report, so I think the answer is "no, there isn't a better way".

I asked on the bug why it's closed if the issue still exists, though.