diff --git a/src/Data/Abstract/Value.hs b/src/Data/Abstract/Value.hs
index 7258bda24..b1d67a3f5 100644
--- a/src/Data/Abstract/Value.hs
+++ b/src/Data/Abstract/Value.hs
@@ -78,6 +78,7 @@ type family LocationFor value :: * where
 
 -- | Value types, e.g. closures, which can root a set of addresses.
 class ValueRoots l v | v -> l where
+  -- | Compute the set of addresses rooted by a given value.
   valueRoots :: v -> Live l v
 
 class AbstractValue v where