The invention relates to a primer composition comprising a compound A1 which contains isocyanate-reactive groups. In order to produce said compound A1, a polyisocyanate A that is provided with at least three isocyanate groups, at least one silane B of formula (I), and a crosslinking agent C comprising at least three isocyanate-reactive functional groups are used. Also disclosed is the use of the inventive primer composition as a primer for adhesives, sealing compounds, or floor coverings, especially one-component moisture-hardening polyurethane adhesives or polyurethane sealing compounds based on polyurethanes or polyurethane-silane hybrids. The inventive primer composition is characterized particularly by excellent adhesion to glass and glass ceramics as well as an extended open time.