An intravascular blood pump (1) comprises a ring seal (10) that is configured to assume a collapsed configuration and an expanded configuration and configured to contact and seal against an inner wall of the patient's blood vessel when inserted therein in the expanded configuration. A support member (12; 13) is disposed inside the ring seal (10) in order to support the ring seal (10) from the inside, wherein the support member (12; 13) is configured to collapse at least partially when a predetermined pressure difference between a proximal area and a distal area of the blood vessel acting on the ring seal (10) is exceeded.