The interim P5+1 deal is finalized, but interpretations of the wording still continue to be a source of dispute, with the talks now stalling over Iran’s installation of test centrifuges.

The pact provides an exemption allowing for new centrifuges for “research and development” purposes, and so far Iran has only installed the new versions in their research tract.

The fact still doesn’t sit well with some P5+1 nations, who interpret the provision differently, saying new centrifuges are only allowed if old ones are taken offline, even if they are for research purposes.

As a practical matter, the distinction means very little, but differences over interpretation could be another excuse for opponents of the pact to start arguing that a violation has taken place. The talks will resume on Monday, and it remains to be seen whether the issue will be allowed to threaten the pact outright.