diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,7 @@
+## v0.2.1
+
+  * Semigroup fix for GHC 8.4 (requires `non-negative` 0.1.2 with same fix)
+
 ## v0.2
 
   * added `TimeSig` type and associated functions, so time signatures
diff --git a/midi-util.cabal b/midi-util.cabal
--- a/midi-util.cabal
+++ b/midi-util.cabal
@@ -1,5 +1,5 @@
 name:                 midi-util
-version:              0.2
+version:              0.2.0.1
 synopsis:             Utility functions for processing MIDI files
 description:
   Common high-level tasks when processing MIDI files.
@@ -26,10 +26,10 @@
   exposed-modules:
     Sound.MIDI.Util
   build-depends:
-    base           >= 4.7   && < 4.9
+    base           >= 4.7   && < 4.12
     , midi         >= 0.2.1 && < 0.3
     , event-list   >= 0.1.1 && < 0.2
-    , non-negative >= 0.1.1 && < 0.2
+    , non-negative >= 0.1.2 && < 0.2
     , containers   >= 0.5.5 && < 0.6
   hs-source-dirs:       src
   default-language:     Haskell2010
diff --git a/src/Sound/MIDI/Util.hs b/src/Sound/MIDI/Util.hs
--- a/src/Sound/MIDI/Util.hs
+++ b/src/Sound/MIDI/Util.hs
@@ -36,6 +36,9 @@
 #if __GLASGOW_HASKELL__ < 710
 import Data.Monoid (Monoid)
 #endif
+#if __GLASGOW_HASKELL__ < 840
+import Data.Semigroup (Semigroup)
+#endif
 import Data.Ratio (denominator)
 
 import qualified Numeric.NonNegative.Wrapper as NN
@@ -77,18 +80,18 @@
 
 -- | Musical time, measured in beats a.k.a. quarter notes.
 newtype Beats = Beats { fromBeats :: NN.Rational }
-  deriving (Eq, Ord, Show, Monoid, NNC.C, Num, Real, Fractional, RealFrac)
+  deriving (Eq, Ord, Show, Semigroup, Monoid, NNC.C, Num, Real, Fractional, RealFrac)
 
 data TimeSig = TimeSig { timeSigLength :: !Beats, timeSigUnit :: !Beats }
   deriving (Eq, Show)
 
 -- | Real time, measured in seconds.
 newtype Seconds = Seconds { fromSeconds :: NN.Rational }
-  deriving (Eq, Ord, Show, Monoid, NNC.C, Num, Real, Fractional, RealFrac)
+  deriving (Eq, Ord, Show, Semigroup, Monoid, NNC.C, Num, Real, Fractional, RealFrac)
 
 -- | A ratio between musical time and real time, measured in beats per second.
 newtype BPS = BPS { fromBPS :: NN.Rational }
-  deriving (Eq, Ord, Show, Monoid, NNC.C, Num, Real, Fractional, RealFrac)
+  deriving (Eq, Ord, Show, Semigroup, Monoid, NNC.C, Num, Real, Fractional, RealFrac)
 
 -- | Creates a tempo as a ratio of a music duration to a real time duration.
 makeTempo :: Beats -> Seconds -> BPS
@@ -341,7 +344,7 @@
 trackTakeZero = fst . trackSplitZero
 
 -- | Drops all events at position zero of the event list.
-trackDropZero :: (NNC.C t) => RTB.T t a -> (RTB.T t a)
+trackDropZero :: (NNC.C t) => RTB.T t a -> RTB.T t a
 trackDropZero = snd . trackSplitZero
 
 -- | Looks for a track name event at position zero.