Abstract: A non-return valve for bore hole sleeves, which are intended for injection of a sealing and/or reinforcing compound into rock cracks and similar cracks and which comprise a rigid case (10), one end (10A) of which is provided with means for detachable connection to the case of a pump hose (12) for the compound to be injected, as well as an expandable device (15) for securing the rigid case in the bore hole (21), comprises an elastic sleeve (22) which is adapted at the other end (10B) of the rigid case (10) in such a way that the rigid case (10) runs into the elastic sleeve (22). The elastic sleeve is adapted for automatical contraction, when no compound is being injected through the elastic sleeve, so that already injected compound can not flow backwards into the rigid case (10). The sleeve (22) is preferably provided with diametrically positioned clamp means (23-26) at its free ends, so that the free end of the sleeve has a flat shape, when no compound is being injected through the elastic sleeve.