1 files changed, 1 insertions, 1 deletions
diff --git a/tree.sig b/tree.sig
index a1ebf86..e06ca68 100644
--- a/tree.sig
+++ b/tree.sig
@@ -11,7 +11,7 @@ signature TREE = sig
 
   val lookup: 'k cmp -> ('k, 'v) t -> 'k -> 'v option
   val lookup2: 'k cmp -> ('k, 'v) t -> 'k ->
-        ('v -> 'v option * 'a) * 'a -> 'a * ('k, 'v) t
+        ('v option -> 'a * 'v option) -> 'a * ('k, 'v) t
 
   val print: ('k, 'v) t -> ('k -> string) -> ('v -> string) -> unit
 end