diff --git a/ascii-case.cabal b/ascii-case.cabal
--- a/ascii-case.cabal
+++ b/ascii-case.cabal
@@ -1,7 +1,7 @@
 cabal-version: 3.0
 
 name: ascii-case
-version: 1.0.0.11
+version: 1.0.1.0
 synopsis: ASCII letter case
 category: Data, Text
 
@@ -33,7 +33,7 @@
 
     build-depends:
         ascii-char ^>= 1.0
-      , base >= 4.13 && < 4.17
+      , base >= 4.14 && < 4.18
 
 library
     import: base
diff --git a/library/ASCII/Case.hs b/library/ASCII/Case.hs
--- a/library/ASCII/Case.hs
+++ b/library/ASCII/Case.hs
@@ -4,7 +4,7 @@
 
 -}
 
-module ASCII.Case ( Case (..), letterCase, isCase, toCase ) where
+module ASCII.Case ( Case (..), letterCase, isCase, toCase, opposite ) where
 
 import ASCII.Char (Char (..))
 import Data.Bool (Bool, otherwise)