diff --git a/semver.cabal b/semver.cabal
--- a/semver.cabal
+++ b/semver.cabal
@@ -1,5 +1,5 @@
 name:                  semver
-version:               0.4.0
+version:               0.4.0.1
 synopsis:              Representation, manipulation, and de/serialisation of Semantic Versions.
 homepage:              https://github.com/brendanhay/semver
 license:               MPL-2.0
diff --git a/src/Data/SemVer/Constraint.hs b/src/Data/SemVer/Constraint.hs
--- a/src/Data/SemVer/Constraint.hs
+++ b/src/Data/SemVer/Constraint.hs
@@ -24,9 +24,10 @@
 
 import           Control.Applicative
 import           Data.Attoparsec.Text
+import           Data.Monoid           ((<>))
 import           Data.SemVer.Internal
-import qualified Data.SemVer.Delimited         as DL
-import           Data.Text                      ( Text )
+import qualified Data.SemVer.Delimited as DL
+import           Data.Text             (Text)
 
 data Constraint
     = CAny