The rules regarding modifications of public contracts were added to EU public procurement law in 2014 in order to clarify the conditions set forth by the relevant case law of the Court of Justice of the European Union. However, the provisions that were ultimately adopted are not quite black and white as one might think. One of the grey areas might be the application of the principle of proportionality to modifications of public contracts. New directives mention proportionality as a principle of "procurement". This article presents a view that contracting authorities shall act in a proportionate manner also after the "procurement" decision has been made, i.e. when a contract has already been awarded.