diff --git a/ShellCheck/ASTLib.hs b/ShellCheck/ASTLib.hs
index 54f8d07..52e0167 100644
--- a/ShellCheck/ASTLib.hs
+++ b/ShellCheck/ASTLib.hs
@@ -23,6 +23,7 @@ import ShellCheck.AST
 
 import Control.Monad.Writer
 import Control.Monad
+import Data.Functor
 import Data.List
 import Data.Maybe