The billionaire investor leading a group of hedge fund managers suing Argentina over a decade-old debt has finally filed to add the claims of over 500 more creditors on top of his original lawsuit.

Consider this Singer's "That's it!" moment.

Here's why:

Argentina technically defaulted last summer after ignoring a US judge's ruling to pay Singer and his cohorts (known collectively as NML) over $1.7 billion in sovereign debt dating from its last default.

One of the excuses Argentina used to explain its recalcitrance was that if it paid NML it would be opening itself up to claims from hundreds more investors because of something called the RUFO clause.