src/HOL/Tools/Nitpick/nitpick_nut.ML

           else if is_built_in_const thy stds x then
             (* FIXME: find out if this case is necessary *)
             Op1 (Not, bool_T, Any, Op2 (Less, bool_T, Any, sub t2, sub t1))
           else
             do_apply t0 ts
-        | (Const (@{const_name nat_gcd}, T), []) => Cst (Gcd, T, Any)
-        | (Const (@{const_name nat_lcm}, T), []) => Cst (Lcm, T, Any)
+        | (Const (@{const_name Nitpick.nat_gcd}, T), []) => Cst (Gcd, T, Any)
+        | (Const (@{const_name Nitpick.nat_lcm}, T), []) => Cst (Lcm, T, Any)
         | (Const (x as (s as @{const_name uminus_class.uminus}, T)), []) =>
           if is_built_in_const thy stds x then
             let val num_T = domain_type T in
               Op2 (Apply, num_T --> num_T, Any,
                    Cst (Subtract, num_T --> num_T --> num_T, Any),

         | (Const (@{const_name is_unknown}, _), [t1]) =>
           Op1 (IsUnknown, bool_T, Any, sub t1)
         | (Const (@{const_name safe_The},
                   Type (@{type_name fun}, [_, T2])), [t1]) =>
           Op1 (SafeThe, T2, Any, sub t1)
-        | (Const (@{const_name Frac}, T), []) => Cst (Fracs, T, Any)
-        | (Const (@{const_name norm_frac}, T), []) => Cst (NormFrac, T, Any)
+        | (Const (@{const_name Nitpick.Frac}, T), []) => Cst (Fracs, T, Any)
+        | (Const (@{const_name Nitpick.norm_frac}, T), []) =>
+          Cst (NormFrac, T, Any)
         | (Const (@{const_name of_nat}, T as @{typ "nat => int"}), []) =>
           Cst (NatToInt, T, Any)
         | (Const (@{const_name of_nat},
                   T as @{typ "unsigned_bit word => signed_bit word"}), []) =>
           Cst (NatToInt, T, Any)