Make dialyzer happier.

V = -1 is a valid tree version.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/ht.erl b/src/ht.erl
index 3af71f8..749bc9e 100644
--- a/src/ht.erl
+++ b/src/ht.erl
@@ -68,7 +68,7 @@ size(#history_tree{version = V}) ->
 new() ->
     #history_tree{version = -1, store = ts:new()}.
 
--spec new(integer()) -> history_tree().
+-spec new(non_neg_integer()) -> history_tree().
 new(Version) ->
     foldl(fun(#mtl{entry = E}, Tree) ->
                   D = (E#timestamped_entry.entry)#plop_entry.data,