diff --git a/brittany.cabal b/brittany.cabal
index 1113f1f..2b22732 100644
--- a/brittany.cabal
+++ b/brittany.cabal
@@ -93,7 +93,7 @@ library {
     , mtl >=2.2.1 && <2.3
     , text >=1.2 && <1.3
     , multistate >=0.7.1.1 && <0.8
-    , syb >=0.6 && <0.7
+    , syb >=0.6 && <0.8
     , neat-interpolation >=0.3.2 && <0.4
     , data-tree-print
     , pretty >=1.1.3.3 && <1.2
diff --git a/stack.yaml b/stack.yaml
index acd6f2c..39c0882 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,8 +1,7 @@
-resolver: lts-8.4
+resolver: lts-9.0
 
 extra-deps:
   - monad-memo-0.4.1
-  - unsafe-0.0
   - czipwith-1.0.0.0
   - butcher-1.1.0.0
   - data-tree-print-0.1.0.0