Abstract: The invention relates to a device for checking for tightness a closure or a connecting weld provided in a flexible fluid-filled hose, which device comprises two clamping members slidable relative to each other, forming in an inserted position a profile with at least one clamping space and an expansion space, as well as folding means, the arrangement being such that at least one hose portion can be folded and clamped in the at least one clamping space, so that the fluid present in the at least one hose portion is pressed to another hose portion including the closure or connecting weld to be checked, which other hose portion can expand in the expansion space.