diff --git a/hspec-core.cabal b/hspec-core.cabal
--- a/hspec-core.cabal
+++ b/hspec-core.cabal
@@ -2,10 +2,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 11851f6559496d43866e59d144cff3a0dc54711f9978991638c367e9e33afb79
+-- hash: cb01400aef82f796965a0ed9071df2f9e3514250f9257e585fe8645646d709bc
 
 name:             hspec-core
-version:          2.4.5
+version:          2.4.6
 license:          MIT
 license-file:     LICENSE
 copyright:        (c) 2011-2017 Simon Hengel,
diff --git a/src/Test/Hspec/Core/Runner.hs b/src/Test/Hspec/Core/Runner.hs
--- a/src/Test/Hspec/Core/Runner.hs
+++ b/src/Test/Hspec/Core/Runner.hs
@@ -228,4 +228,9 @@
 
 instance Monoid Summary where
   mempty = Summary 0 0
+#if !MIN_VERSION_base(4,11,0)
   (Summary x1 x2) `mappend` (Summary y1 y2) = Summary (x1 + y1) (x2 + y2)
+#else
+instance Semigroup Summary where
+  (Summary x1 x2) <> (Summary y1 y2) = Summary (x1 + y1) (x2 + y2)
+#endif