diff --git a/src/Data/Query.hs b/src/Data/Query.hs
index ad121a6..4ccd18b 100644
--- a/src/Data/Query.hs
+++ b/src/Data/Query.hs
@@ -29,18 +29,18 @@ data Field a where
   Title :: Field String
 
 data QueryF f where
-  StartsWith :: Field a -> a -> QueryF f
-  EndsWith :: Field a -> a -> QueryF f
+  StartsWith :: Field String -> String -> QueryF f
+  EndsWith :: Field String -> String -> QueryF f
   And :: f -> f -> QueryF f
 
 deriving instance Functor QueryF
 
 type Query = Fix QueryF
 
-startsWith :: Field a -> a -> Query
+startsWith :: Field String -> String -> Query
 startsWith field x = Fix (StartsWith field x)
 
-endsWith :: Field a -> a -> Query
+endsWith :: Field String -> String -> Query
 endsWith field x = Fix (EndsWith field x)
 
 (.&&.) :: Query -> Query -> Query