diff --git a/audacity.cabal b/audacity.cabal
--- a/audacity.cabal
+++ b/audacity.cabal
@@ -1,5 +1,5 @@
 Name:                audacity
-Version:             0.0.2.3
+Version:             0.0.2.4
 Synopsis:            Interchange with the Audacity sound signal editor
 Description:
   This package provides functions
@@ -41,7 +41,7 @@
 Cabal-Version:       >=1.10
 
 Source-Repository this
-  Tag:         0.0.2.3
+  Tag:         0.0.2.4
   Type:        darcs
   Location:    https://hub.darcs.net/thielema/audacity
 
@@ -78,7 +78,7 @@
     semigroups >=0.1 && <1,
     transformers >=0.3 && <0.7,
     deepseq >=1.3 && <1.7,
-    base >=4.5 && <5
+    base >=4.11 && <5
   Hs-Source-Dirs:      src
   Default-Language:    Haskell2010
   GHC-Options:         -Wall
diff --git a/src/Sound/Audacity/LabelTrack.hs b/src/Sound/Audacity/LabelTrack.hs
--- a/src/Sound/Audacity/LabelTrack.hs
+++ b/src/Sound/Audacity/LabelTrack.hs
@@ -44,7 +44,6 @@
 
 instance Mn.Monoid (T time label) where
    mempty = empty
-   mappend (Cons xs) (Cons ys) = Cons $ xs ++ ys
    mconcat = Cons . concatMap decons
 
 instance (NFData time, NFData label) => NFData (T time label) where