diff --git a/validator_derive/Cargo.toml b/validator_derive/Cargo.toml
index 58e0de56..e10dc459 100644
--- a/validator_derive/Cargo.toml
+++ b/validator_derive/Cargo.toml
@@ -19,7 +19,7 @@ syn = "2"
 quote = "1"
 proc-macro2 = "1"
 proc-macro-error2 = "2"
-darling = { version = "0.20", features = ["suggestions"] }
+darling = { version = "0.21", features = ["suggestions"] }
 
 [features]
 nightly_features = ["proc-macro-error2/nightly"]
diff --git a/validator_derive_tests/tests/compile-fail/custom/defined_args_in_custom.stderr b/validator_derive_tests/tests/compile-fail/custom/defined_args_in_custom.stderr
index 5bd35ebf..43295beb 100644
--- a/validator_derive_tests/tests/compile-fail/custom/defined_args_in_custom.stderr
+++ b/validator_derive_tests/tests/compile-fail/custom/defined_args_in_custom.stderr
@@ -1,4 +1,4 @@
-error: Unknown field: `arg`
+error: Unknown field: `arg`. Available values: `code`, `function`, `message`, `use_context`
  --> tests/compile-fail/custom/defined_args_in_custom.rs:5:49
   |
 5 |     #[validate(custom(function = "hello_world", arg = "(i64, i64)"))]