Remove nil values from a map?

I have a Clojure map that may contain values that are nil and I'm trying to write a function to remove them, without much success (I'm new to this).

E.g.:

(def record {:a 1 :b 2 :c nil})
(merge (for [[k v] record :when (not (nil? v))] {k v}))

This results in a sequence of maps, which isn't what I expected from merge:

({:a 1} {:b 2})

I would like to have:

{:a 1, :b 2}