diff --git a/src/ShellCheck/Formatter/JSON.hs b/src/ShellCheck/Formatter/JSON.hs
index 7613a1f..490a06b 100644
--- a/src/ShellCheck/Formatter/JSON.hs
+++ b/src/ShellCheck/Formatter/JSON.hs
@@ -25,6 +25,7 @@ import ShellCheck.Formatter.Format
 
 import Data.Aeson
 import Data.IORef
+import Data.Monoid
 import GHC.Exts
 import System.IO
 import qualified Data.ByteString.Lazy.Char8 as BL