The invention discloses a hairspring with a device to prevent coils from moving close together. The invention relates to a hairspring comprising a leaf having a polygonal cross-section which is wound onto itself in a plurality of coils. According to the invention, at least one coil comprises a device for preventing coils from moving close together including at least four abutments mounted on a single surface and projecting from the body of said at least one coil of the leaf, each one of said at least four abutments being arranged such as to engage with the facing surface of another coil of the leaf while preventing the other coil from touching said at least one coil in the event of an impact.