src/HOL/Tools/Nitpick/nitpick_nut.ML

         | (Const (@{const_name "op ="}, T), [t1, t2]) => sub_equals T t1 t2
         | (Const (@{const_name "op &"}, _), [t1, t2]) =>
           Op2 (And, bool_T, Any, sub' t1, sub' t2)
         | (Const (@{const_name "op |"}, _), [t1, t2]) =>
           Op2 (Or, bool_T, Any, sub t1, sub t2)
-        | (Const (@{const_name "op -->"}, _), [t1, t2]) =>
+        | (Const (@{const_name HOL.implies}, _), [t1, t2]) =>
           Op2 (Or, bool_T, Any, Op1 (Not, bool_T, Any, sub t1), sub' t2)
         | (Const (@{const_name If}, T), [t1, t2, t3]) =>
           Op3 (If, nth_range_type 3 T, Any, sub t1, sub t2, sub t3)
         | (Const (@{const_name Let}, T), [t1, Abs (s, T', t2)]) =>
           Op3 (Let, nth_range_type 2 T, Any, BoundName (length Ts, T', Any, s),