diff --git a/CHANGES b/CHANGES
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,7 @@
+* 0.2.1.1: 5 April 2018
+
+- allow base-4.11 for GHC-8.4
+
 * 0.2.1: 3 July 2017
 
 - migrate from newtype to newtype-generics dependency
diff --git a/dual-tree.cabal b/dual-tree.cabal
--- a/dual-tree.cabal
+++ b/dual-tree.cabal
@@ -1,5 +1,5 @@
 name:                dual-tree
-version:             0.2.1
+version:             0.2.1.1
 synopsis:            Rose trees with cached and accumulating monoidal annotations
 description:         Rose (n-ary) trees with both upwards- (/i.e./
                      cached) and downwards-traveling (/i.e./
@@ -8,20 +8,20 @@
                      the @diagrams@ framework
                      (<http://projects.haskell.org/diagrams>), but
                      potentially has other applications as well.
-		     .
+                     .
                      Abstractly, a DUALTree is a rose (n-ary) tree
                      with data (of type @l@) at leaves, data (of type
                      @a@) at internal nodes, and two types of monoidal
                      annotations, one (of type @u@) travelling \"up\"
                      the tree and one (of type @d@) traveling
                      \"down\".
-		     .
-		     See "Data.Tree.DUAL" for full documentation.
-		     "Data.Tree.DUAL" provides a public API which
-		     should suffice for most purposes.
-		     "Data.Tree.DUAL.Internal" exports more of the
-		     internal implementation---use it at your own
-		     risk.
+                     .
+                     See "Data.Tree.DUAL" for full documentation.
+                     "Data.Tree.DUAL" provides a public API which
+                     should suffice for most purposes.
+                     "Data.Tree.DUAL.Internal" exports more of the
+                     internal implementation---use it at your own
+                     risk.
 license:             BSD3
 license-file:        LICENSE
 extra-source-files:  CHANGES
@@ -31,7 +31,7 @@
 build-type:          Simple
 cabal-version:       >=1.10
 bug-reports:         https://github.com/diagrams/dual-tree/issues
-tested-with:         GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1
+tested-with:         GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1, GHC == 8.2.2, GHC == 8.4.1
 source-repository head
   type: git
   location: https://github.com/diagrams/dual-tree.git
@@ -40,7 +40,7 @@
   default-language:  Haskell2010
   exposed-modules:   Data.Tree.DUAL
                      Data.Tree.DUAL.Internal
-  build-depends:     base >= 4.3 && < 4.11,
+  build-depends:     base >= 4.3 && < 4.12,
                      semigroups >= 0.8 && < 0.19,
                      newtype-generics >= 0.5 && < 0.6,
                      monoid-extras >= 0.2 && < 0.5