diff --git a/pred-trie.cabal b/pred-trie.cabal
--- a/pred-trie.cabal
+++ b/pred-trie.cabal
@@ -1,5 +1,5 @@
 Name:                   pred-trie
-Version:                0.0.7
+Version:                0.0.7.1
 Author:                 Athan Clark <athan.clark@gmail.com>
 Maintainer:             Athan Clark <athan.clark@gmail.com>
 License:                BSD3
diff --git a/src/Data/Trie/Pred/Unified.hs b/src/Data/Trie/Pred/Unified.hs
--- a/src/Data/Trie/Pred/Unified.hs
+++ b/src/Data/Trie/Pred/Unified.hs
@@ -22,7 +22,7 @@
 
 merge :: (Eq t) => RUPTrie t x -> RUPTrie t x -> RUPTrie t x
 merge (Rooted mx xs) (Rooted my ys) =
-  Rooted my $ foldr go [] $ xs ++ ys
+  Rooted (getLast $ Last mx <> Last my) $ foldr go [] $ xs ++ ys
   where
     go :: (Eq t) => UPTrie t x -> [UPTrie t x] -> [UPTrie t x]
     go a [] = [a]