diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## Modern URI 0.1.1.1
+
+* Fixed implementation of `Text.URI.Lens.queryParam` traversal.
+
 ## Modern URI 0.1.1.0
 
 * Derived `NFData` for `ParseException`.
diff --git a/Text/URI.hs b/Text/URI.hs
--- a/Text/URI.hs
+++ b/Text/URI.hs
@@ -45,9 +45,11 @@
   , unRText
   , RTextException (..)
     -- * Parsing
+    -- $parsing
   , parser
   , parserBs
     -- * Rendering
+    -- $rendering
   , render
   , render'
   , renderBs
@@ -75,3 +77,14 @@
 -- it rejects it by throwing the 'RTextException'. Remember that the 'Maybe'
 -- datatype is also an instance of 'Control.Monad.Catch.MonadThrow', and so
 -- one could as well use the smart constructors in the 'Maybe' monad.
+
+-- $parsing
+--
+-- The input you feed into the parsers must be a valid URI as per RFC 3986,
+-- that is, its components should be percent-encoded where necessary.
+
+-- $rendering
+--
+-- Rendering functions take care of constructing correct 'URI'
+-- representation as per RFC 3986, that is, percent-encoding will be applied
+-- when necessary automatically.
diff --git a/Text/URI/Lens.hs b/Text/URI/Lens.hs
--- a/Text/URI/Lens.hs
+++ b/Text/URI/Lens.hs
@@ -131,13 +131,13 @@
 -- return\/modify several items at once.
 
 queryParam :: RText 'QueryKey -> Traversal' [URI.QueryParam] (RText 'QueryValue)
-queryParam k f s = go s
+queryParam k f = traverse g
   where
-    go []     = pure s
-    go (x:xs) =
-      case x of
-        QueryParam k' v -> if k == k' then f v *> go xs else go xs
-        _               -> go xs
+    g p@(QueryParam k' v) =
+      if k == k'
+        then QueryParam k' <$> f v
+        else pure p
+    g p = pure p
 
 -- | A getter that can project 'Text' from refined text values.
 
diff --git a/Text/URI/Parser/Text.hs b/Text/URI/Parser/Text.hs
--- a/Text/URI/Parser/Text.hs
+++ b/Text/URI/Parser/Text.hs
@@ -35,8 +35,10 @@
 import qualified Data.Text.Encoding         as TE
 import qualified Text.Megaparsec.Char.Lexer as L
 
--- | Construct a 'URI' from 'Text'. In case of failure 'ParseException' is
--- thrown.
+-- | Construct a 'URI' from 'Text'. The input you pass to 'mkURI' must be a
+-- valid URI as per RFC 3986, that is, its components should be
+-- percent-encoded where necessary. In case of parse failure
+-- 'ParseException' is thrown.
 --
 -- This function uses the 'parser' parser under the hood, which you can also
 -- use directly in a Megaparsec parser.
diff --git a/modern-uri.cabal b/modern-uri.cabal
--- a/modern-uri.cabal
+++ b/modern-uri.cabal
@@ -1,5 +1,5 @@
 name:                 modern-uri
-version:              0.1.1.0
+version:              0.1.1.1
 cabal-version:        >= 1.18
 tested-with:          GHC==7.10.3, GHC==8.0.2, GHC==8.2.1
 license:              BSD3