Saving symbols causes invalid metadata header

[Brandon Cuff]

I'm using Mono.Cecil to add some generated types to an assembly. I would like to preserve the debug information. However when I load and store symbols using Mono.Cecil.Pdb, the assembly's metadata header gets messed up. Reflector produces this message - "Common.Test, Invalid 'BSJB' signature in Metadata header." I generated one assembly with symbols and one without and compared the two and noticed a slight difference in the headers.

Any idea why they're being written differently?

Thanks,
 - Brandon