diff --git a/src/SysCmd.hs b/src/SysCmd.hs
index a40c9f0..cda89a7 100644
--- a/src/SysCmd.hs
+++ b/src/SysCmd.hs
@@ -162,5 +162,9 @@ s +-+ t | last s == ' ' = s ++ t
         | head t == ' ' = s ++ t
 s +-+ t = s ++ " " ++ t
 
+#if (defined(MIN_VERSION_base) && MIN_VERSION_base(4,8,2))
 notNull :: Foldable t => t a -> Bool
+#else
+notNull :: [a] -> Bool
+#endif
 notNull = not . null