diff --git a/lib/Options/Tokenize.hs b/lib/Options/Tokenize.hs
--- a/lib/Options/Tokenize.hs
+++ b/lib/Options/Tokenize.hs
@@ -120,8 +120,9 @@
 	, stLongKeys = Data.Map.unionWith unionKeys (stLongKeys st) (toLongKeys opts)
 	}
 
+-- note: unionKeys assumes that the OptionInfo is equivalent in both maps.
 unionKeys :: ([OptionKey], OptionInfo) -> ([OptionKey], OptionInfo) -> ([OptionKey], OptionInfo)
-unionKeys = undefined
+unionKeys (keys1, info) (keys2,_) = (keys1++keys2, info)
 
 parseLong :: String -> Tok ()
 parseLong optName = do
diff --git a/options.cabal b/options.cabal
--- a/options.cabal
+++ b/options.cabal
@@ -1,5 +1,5 @@
 name: options
-version: 1.2
+version: 1.2.1
 license: MIT
 license-file: license.txt
 author: John Millikin <john@john-millikin.com>
@@ -78,7 +78,7 @@
 source-repository this
   type: git
   location: https://john-millikin.com/code/haskell-options/
-  tag: haskell-options_1.2
+  tag: haskell-options_1.2.1
 
 library
   ghc-options: -Wall -O2