The need to revise the eurozone fiscal rules now seems widely accepted and many amendments are being discussed. They are still meant to impose discipline on governments’ financial behaviour but are trying to define smarter ways to constrain public deficits or spending. The purpose of this policy insight is neither to dispute the need for fiscal discipline nor to formulate a new proposal to enforce it. It is rather to draw attention to an often-overlooked issue that has come to the forefront during the last decade: when monetary policy has lost most of its leverage on private demand, trying to meet a fiscal target that does not take into account the spending behaviour of private agents can unduly constrain economic activity.