diff --git a/Data/Loc.hs b/Data/Loc.hs
--- a/Data/Loc.hs
+++ b/Data/Loc.hs
@@ -50,6 +50,9 @@
 import Data.Typeable (Typeable(..))
 import Data.List (foldl')
 import Data.Monoid (Monoid(..))
+#if MIN_VERSION_base(4,9,0) && !(MIN_VERSION_base(4,11,0))
+import Data.Semigroup (Semigroup(..))
+#endif
 
 -- | Position type.
 data Pos = -- | Source file name, line, column, and character offset.
@@ -130,12 +133,22 @@
 locEnd  NoLoc      = NoLoc
 locEnd  (Loc _ p)  = Loc p p
 
+-- | Append two locations.
+locAppend :: Loc -> Loc -> Loc
+locAppend NoLoc       l           = l
+locAppend l           NoLoc       = l
+locAppend (Loc b1 e1) (Loc b2 e2) = Loc (min b1 b2) (max e1 e2)
+
+#if MIN_VERSION_base(4,9,0)
+instance Semigroup Loc where
+    (<>) = locAppend
+#endif
+
 instance Monoid Loc where
     mempty = NoLoc
-
-    NoLoc     `mappend` l         = l
-    l         `mappend` NoLoc     = l
-    Loc b1 e1 `mappend` Loc b2 e2 = Loc (min b1 b2) (max e1 e2)
+#if !(MIN_VERSION_base(4,11,0))
+    mappend = locAppend
+#endif
 
 -- | Merge the locations of two 'Located' values.
 (<-->) :: (Located a, Located b) => a -> b -> Loc
@@ -147,6 +160,11 @@
 -- to be compared modulo location information.
 newtype SrcLoc = SrcLoc Loc
   deriving (Monoid, Data, Typeable)
+
+#if MIN_VERSION_base(4,9,0)
+instance Semigroup SrcLoc where
+  SrcLoc l1 <> SrcLoc l2 = SrcLoc (l1 <> l2)
+#endif
 
 instance Eq SrcLoc where
     _ == _ = True
diff --git a/srcloc.cabal b/srcloc.cabal
--- a/srcloc.cabal
+++ b/srcloc.cabal
@@ -1,10 +1,10 @@
 name:           srcloc
-version:        0.5.1.1
+version:        0.5.1.2
 cabal-version:  >= 1.6
 license:        BSD3
 license-file:   LICENSE
 copyright:      (c) 2006-2011 Harvard University
-                (c) 2011-2017 Geoffrey Mainland
+                (c) 2011-2018 Geoffrey Mainland
 author:         Geoffrey Mainland <mainland@drexel.edu>
 maintainer:     Geoffrey Mainland <mainland@drexel.edu>
 stability:      alpha
@@ -12,7 +12,8 @@
 category:       Data
 synopsis:       Data types for managing source code locations.
 description:    Data types for tracking, combining, and printing source code locations.
-tested-with:    GHC==7.4.2, GHC==7.6.3, GHC==7.8.3, GHC==7.10.3, GHC==8.0.2, GHC==8.2.1
+tested-with:    GHC==7.4.2, GHC==7.6.3, GHC==7.8.3, GHC==7.10.3, GHC==8.0.2,
+                GHC==8.2.2, GHC==8.4.1
 
 build-type:     Simple