Economic Security in the Road to Serfdom

In the road to Serfdom Hayek identifies two types of Economic Security....the first he terms as Limited Security where individuals are protected against "physical privation and a given minimum sustenance for all".....the second he describes as the "security of a minimum income and the security of the particular income a person is thought to deserve" ...what he later describes as the provision of the certainty of a given income Could someone please explain why the second type of security described by Hayek is incompatible with a liberal market economy. Thank You