A fixing device for mounting wall elements for constructing a wall, includes: a support profile, A securing element which is designed to extend between the wall elements and can be twisted relative to the support profile between a first position in which an engagement element of the securing element remains separate from the support profile, and a second position in which the engagement element engages on the support profile for fixing and secures the wall elements; and a closing profile which in the second position is attachable to the securing element and comprises a blocking element for preventing the securing element from twisting back.