Abstract: A catalyst bed configuration, in particular for olefin conversion by metathesis, comprising at least one main catalyst bed comprising a) at least one first catalyst component comprising a metathesis catalyst, and b) at least one second catalyst component comprising a catalyst for double bond isomerisation, whereby the first and second catalyst are intimate mixed with each other, and at least one catalyst pre-bed arranged upstream of the at least one main catalyst bed comprising at least one compound selected from the group of alkaline earth oxides. The mass ratio of the at least one catalyst pre-bed to the at least one main catalyst bed is between 1:2 and 2.5:1, preferably between 1:1.5 and 2.5:1, more preferably between 1:1 and 2.5:1, most preferably between 1:1 and 2:1.