A composition for sealing/coating the edges of wood-fibre boards is provided. The composition includes at least one compound of general formula R1aSiX(4-a) (I), and/or their hydrolysis products. X is H, OH or a hydrolyzable group selected from alkoxy-, aryloxy-, and acyloxy-, R1 is an organic radical selected from the group including alkyl, aryl, and cycloalkyl, and R1 has at least one functional group Q1 selected from a hydroxy, amino, monoalkylamino, carboxy, mercapto, alkoxy, aldehyde, acrylic, acryloxy, methacrylic, methacryloxy, cyano, isocyano and epoxy group, and a=0, 1, 2, 3, The composition also includes at least one compound of general formula R2bSiX(4-b) (II), and/or their hydrolysis products. X has the above meaning, R2 is a non-hydrolyzable organic radical selected from alkyl, aryl, alkenyl, alkynyl, cycloalkyl, and cycloalkenyl, and b=1, 2, 3, or 4. The composition also includes at least one aqueous polymer dispersion.