A composition, including at least one silane group-containing polymer that is liquid at room temperature, at least one epoxide liquid resin, and at least one aliphatic polyamine having a molecular weight of at least 115 g/mol and having at least three amine hydrogens reactive toward epoxide groups. The composition is a liquid that is configured to form a sealing membrane after curing. The sealing film applied in liquid form is isocyanate-free, low-odor, and easy to process because of the low viscosity and the long open time. The sealing film cures quickly and forms a high-quality elastic material having good mechanical properties and good weather resistance.