diff --git a/casr-logbook.cabal b/casr-logbook.cabal
--- a/casr-logbook.cabal
+++ b/casr-logbook.cabal
@@ -1,5 +1,5 @@
 name:               casr-logbook
-version:            0.5.0
+version:            0.5.1
 license:            OtherLicense
 license-file:       LICENSE
 author:             Tony Morris <ʇǝu˙sıɹɹoɯʇ@ןןǝʞsɐɥ>
diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,3 +1,7 @@
+0.5.1
+
+* `Semigroup` instance for later GHC versions.
+
 0.5.0
 
 * update `digit` package.
diff --git a/src/Data/Aviation/Casr/Logbook/Types/TimeAmount.hs b/src/Data/Aviation/Casr/Logbook/Types/TimeAmount.hs
--- a/src/Data/Aviation/Casr/Logbook/Types/TimeAmount.hs
+++ b/src/Data/Aviation/Casr/Logbook/Types/TimeAmount.hs
@@ -13,6 +13,7 @@
 import Data.Bool(Bool, bool)
 import Data.Maybe(fromMaybe)
 import Data.Ord((>))
+import Data.Semigroup
 import Prelude(Integral, divMod, mod)
 import Control.Lens(makeClassy, (^?), over, _1, ( # ))
 import Data.Eq(Eq)
@@ -55,11 +56,15 @@
 timeAmountBy10 (TimeAmount a b) =
   a * 10 + integralDecimal # b
 
+instance Semigroup TimeAmount where
+  (<>) =
+    addtimeamount
+
 instance Monoid TimeAmount where
   mempty =
     zerotimeamount
   mappend =
-    addtimeamount
+    (<>)
 
 ---- belongs in digit package