We consider elastomer composites with fillers made of a material that exhibits negative coefficient of thermal expansion (CTE). Such fillers provide an opportunity to reduce the thermal shrinkage of the composite in cooling. It is especially relevant in sealing applications for structures operated at low temperatures. It is known that CTE of rubber is at least an order of magnitude higher than that of steel. Due to this fact, an elastomer seal compressed in its groove may lose interference with the mating steel surface upon temperature drop and, thus, form a leak path for the contained fluids like hydrocarbons. In the present paper we start with estimates of the contact pressure drop in a typical O-ring rubber seal caused by cooling. Then we investigate how the volume fraction and the shape of filler particles affect thermo-elastic properties and the sealing performance of the composite. We demonstrate that the contact pressure drop due to freezing down to (Formula presented.) can be reduced twice in the case of spherical inclusions, and the effect can be significantly enhanced by changing the shape of the filler particles. Finally, having in mind the strain fracture criterion, we estimate local strains at the interface between elastomer and filler considering various shapes of the filler particles.