A method of sealing an optionally pre-coated substrate comprising at least step and optionally also step, namely optionally applying a primer composition at least in portion onto a surface of an optionally pre-coated substrate to form a primer film at least in portion on said surface, applying a sealant composition at least in portion onto a surface of an optionally pre-coated substrate in case optional step is not performed or onto the primer film in case optional step is performed, wherein the sealant composition is different from the primer composition optionally applied in step and is obtainable by mixing the components of a sealing system with each other, said sealing system being a two-component sealing system comprising two components and being separate from each other, wherein component of the sealing system comprises at least one polymeric constituent containing two or more thiol groups selected from polyether, polythioether, polysulfide, polythioether-sulfide constituents and mixtures thereof, and wherein component of the sealing system comprises at least one constituent (b), which is suitable for hardening the sealant composition by at least partially inducing a chemical transformation of the two or more thiol groups of constituent, characterized in that at least one organosilane constituent, which contains (i) at least one hydrolyzable group X, (ii) at least one isocyanate group, and (iii) a spacer unit positioned between the at least one hydrolyzable group X and the at least one isocyanate group, wherein said spacer unit comprises at least one moiety MS, which comprises at least one sulfur atom, is at least present - when optional step is not performed - as constituent in component of the sealing system used for preparing the sealant composition applied in step or is - when step is performed - at least present as a constituent in the primer composition applied in step. optionally applying a primer composition at least in portion onto a surface of an optionally pre-coated substrate to form a primer film at least in portion on said surface, applying a sealant composition at least in portion onto a surface of an optionally pre-coated substrate in case optional step is not performed or onto the primer film in case optional step is performed, wherein the sealant composition is different from the primer composition optionally applied in step and is obtainable by mixing the components of a sealing system with each other, said sealing system being a two-component sealing system comprising two components and being separate from each other, wherein component of the sealing system comprises at least one polymeric constituent containing two or more thiol groups selected from polyether, polythioether, polysulfide, polythioether-sulfide constituents and mixtures thereof, and wherein component of the sealing system comprises at least one constituent (b), which is suitable for hardening the sealant composition by at least partially inducing a chemical transformation of the two or more thiol groups of constituent, wherein component of the sealing system comprises at least one polymeric constituent containing two or more thiol groups selected from polyether, polythioether, polysulfide, polythioether-sulfide constituents and mixtures thereof, and wherein component of the sealing system comprises at least one constituent (b), which is suitable for hardening the sealant composition by at least partially inducing a chemical transformation of the two or more thiol groups of constituent, characterized in that at least one organosilane constituent, which contains (i) at least one hydrolyzable group X, (ii) at least one isocyanate group, and (iii) a spacer unit positioned between the at least one hydrolyzable group X and the at least one isocyanate group, wherein said spacer unit comprises at least one moiety MS, which comprises at least one sulfur atom, (i) at least one hydrolyzable group X, (ii) at least one isocyanate group, and (iii) a spacer unit positioned between the at least one hydrolyzable group X and the at least one isocyanate group, wherein said spacer unit comprises at least one moiety MS, which comprises at least one sulfur atom, is at least present - when optional step is not performed - as constituent in component of the sealing system used for preparing the sealant composition applied in step or is - when step is performed - at least present as a constituent in the primer composition applied in step.