diff --git a/Geom2D/CubicBezier/Basic.hs b/Geom2D/CubicBezier/Basic.hs
--- a/Geom2D/CubicBezier/Basic.hs
+++ b/Geom2D/CubicBezier/Basic.hs
@@ -1,5 +1,5 @@
 {-# LANGUAGE PatternGuards #-}
-{-# LANGUAGE BangPatterns, FlexibleInstances, MultiParamTypeClasses, DeriveTraversable, ViewPatterns, PatternSynonyms, MultiWayIf #-}
+{-# LANGUAGE BangPatterns, CPP, FlexibleInstances, MultiParamTypeClasses, DeriveTraversable, ViewPatterns, PatternSynonyms, MultiWayIf #-}
 module Geom2D.CubicBezier.Basic
        (CubicBezier (..), QuadBezier (..), AnyBezier (..), GenericBezier(..),
         PathJoin (..), ClosedPath(..), OpenPath (..), AffineTransform (..), anyToCubic, anyToQuad,
@@ -16,6 +16,9 @@
 import Math.BernsteinPoly
 import Numeric.Integration.TanhSinh
 import Data.Monoid ()
+#if !MIN_VERSION_base(4,11,0)
+import Data.Semigroup (Semigroup(..))
+#endif
 import Data.List (minimumBy)
 import Data.Function (on)
 import Data.VectorSpace
@@ -93,12 +96,17 @@
 data ClosedPath a = ClosedPath [(Point a, PathJoin a)]
                   deriving (Show, Functor, Foldable, Traversable)
 
+instance Semigroup (OpenPath a) where
+  p1 <> OpenPath [] _ = p1
+  OpenPath [] _ <> p2 = p2
+  OpenPath joins1 _ <> OpenPath joins2 p =
+    OpenPath (joins1 ++ joins2) p
+
 instance Monoid (OpenPath a) where
   mempty = OpenPath [] (error "empty path")
-  mappend p1 (OpenPath [] _) = p1
-  mappend (OpenPath [] _) p2 = p2
-  mappend (OpenPath joins1 _) (OpenPath joins2 p) =
-    OpenPath (joins1 ++ joins2) p
+#if !MIN_VERSION_base(4,11,0)
+  mappend = (<>)
+#endif
 
 instance (Num a) => AffineTransform (PathJoin a) a where
   transform _ JoinLine = JoinLine
diff --git a/cubicbezier.cabal b/cubicbezier.cabal
--- a/cubicbezier.cabal
+++ b/cubicbezier.cabal
@@ -1,5 +1,5 @@
 Name:		cubicbezier
-Version: 	0.6.0.4
+Version: 	0.6.0.5
 Synopsis:	Efficient manipulating of 2D cubic bezier curves.
 Category: 	Graphics, Geometry, Typography
 Copyright: 	Kristof Bastiaensen (2017)
@@ -36,6 +36,8 @@
   Build-depends: base >= 4.8 && < 5, containers >= 0.5.3, integration >= 0.1.1, vector >= 0.10,
                  matrices >= 0.4.1, microlens >= 0.1.2, microlens-th >= 0.1.2, microlens-mtl >= 0.1.2, mtl >= 2.1.1,
                  fast-math >= 1.0.0, vector-space >= 0.10.4
+  if !impl(ghc>=8.0)
+    Build-depends: semigroups >= 0.16
   Exposed-Modules:
     Geom2D
     Geom2D.CubicBezier