diff --git a/reactive-midyim.cabal b/reactive-midyim.cabal
--- a/reactive-midyim.cabal
+++ b/reactive-midyim.cabal
@@ -1,5 +1,5 @@
 Name:             reactive-midyim
-Version:          0.4.1.2
+Version:          0.4.1.3
 License:          BSD3
 License-File:     LICENSE
 Author:           Henning Thielemann <haskell@henning-thielemann.de>
@@ -44,7 +44,7 @@
 Source-Repository this
   type:     darcs
   location: https://hub.darcs.net/thielema/reactive-midyim/
-  tag:      0.4.1.2
+  tag:      0.4.1.3
 
 Library
   Build-Depends:
@@ -59,7 +59,7 @@
     transformers >=0.2 && <0.7,
     semigroups >=0.1 && <1,
     random >=1 && <2,
-    base >=4 && <5
+    base >=4.11 && <5
 
   Default-Language: Haskell98
   GHC-Options:      -Wall
diff --git a/src/Reactive/Banana/MIDI/Process.hs b/src/Reactive/Banana/MIDI/Process.hs
--- a/src/Reactive/Banana/MIDI/Process.hs
+++ b/src/Reactive/Banana/MIDI/Process.hs
@@ -448,11 +448,6 @@
    xs <- RBF.plainChanges x
    fmap RB.filterJust $
       flip RBU.mapAdjacent x0 (\old new -> toMaybe (new/=old) new) xs
---   return xs
-{-
-   return $ RB.filterJust $ fst $
-      RB.mapAccum x0 $ fmap (\new old -> (toMaybe (new/=old) new, new)) xs
--}
 
 
 sweep ::
diff --git a/src/Reactive/Banana/MIDI/Time.hs b/src/Reactive/Banana/MIDI/Time.hs
--- a/src/Reactive/Banana/MIDI/Time.hs
+++ b/src/Reactive/Banana/MIDI/Time.hs
@@ -5,7 +5,7 @@
 import qualified Numeric.NonNegative.Class as NonNeg
 
 import Control.Applicative (Const(Const), )
-import Data.Monoid (Monoid, mempty, mappend, )
+import Data.Monoid (Monoid, mempty, )
 import Data.Semigroup (Semigroup, (<>), )
 import Data.Tuple.HT (mapPair, mapSnd, )
 import Data.Ord.HT (comparing, )
@@ -62,14 +62,12 @@
 
 instance Monoid Seconds where
    mempty = Seconds 0
-   mappend = (<>)
 
 instance Semigroup Ticks where
    Ticks x <> Ticks y = Ticks $ x+y
 
 instance Monoid Ticks where
    mempty = Ticks 0
-   mappend = (<>)
 
 
 instance (Semigroup a) => Semigroup (T m t a) where
@@ -77,7 +75,6 @@
 
 instance (Monoid a) => Monoid (T m t a) where
    mempty = cons mempty
-   mappend x y = cons $ mappend (decons x) (decons y)
 
 
 class RelativeC t where
@@ -122,9 +119,9 @@
      else error $ msg ++ ": negative number"
 
 inc ::
-   (Monoid a) =>
+   (Semigroup a) =>
    T m Relative a -> T m t a -> T m t a
-inc dt t = cons $ mappend (decons t) (decons dt)
+inc dt t = cons $ decons t <> decons dt
 
 subSat ::
    Split a => T m t a -> T m t a -> T m Relative a