diff --git a/mandrill.cabal b/mandrill.cabal
--- a/mandrill.cabal
+++ b/mandrill.cabal
@@ -1,5 +1,5 @@
 name:                mandrill
-version:             0.5.3.5
+version:             0.5.3.6
 synopsis:            Library for interfacing with the Mandrill JSON API
 description:         Pure Haskell client for the Mandrill JSON API
 license:             MIT
@@ -41,7 +41,7 @@
     , http-types >= 0.8.0
     , http-client >= 0.3.0
     , http-client-tls >= 0.2.0.0
-    , aeson >= 0.7.0.3 && < 1.4.0.0
+    , aeson >= 0.7.0.3 && < 1.5.0.0
     , microlens-th >= 0.4.0.0
     , blaze-html >= 0.5.0.0
     , QuickCheck >= 2.6 && < 3.0
diff --git a/src/Network/API/Mandrill/Types.hs b/src/Network/API/Mandrill/Types.hs
--- a/src/Network/API/Mandrill/Types.hs
+++ b/src/Network/API/Mandrill/Types.hs
@@ -158,6 +158,11 @@
 mkMandrillHtml :: Blaze.Html -> MandrillHtml
 mkMandrillHtml = MandrillHtml
 
+#if MIN_VERSION_base(4,11,0)
+instance Semigroup MandrillHtml where
+  MandrillHtml m1 <> MandrillHtml m2 = MandrillHtml (m1 <> m2)
+#endif
+
 instance Monoid MandrillHtml where
   mempty = MandrillHtml mempty
   mappend (MandrillHtml m1) (MandrillHtml m2) = MandrillHtml (m1 <> m2)