diff --git a/substrate/frame/uniques/src/functions.rs b/substrate/frame/uniques/src/functions.rs
index 5d573e4209..40c436bd56 100644
--- a/substrate/frame/uniques/src/functions.rs
+++ b/substrate/frame/uniques/src/functions.rs
@@ -31,10 +31,11 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 			&mut InstanceDetailsFor<T, I>,
 		) -> DispatchResult,
 	) -> DispatchResult {
-		let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+		let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 		ensure!(!class_details.is_frozen, Error::<T, I>::Frozen);
 
-		let mut details = Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
+		let mut details =
+			Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::UnknownClass)?;
 		ensure!(!details.is_frozen, Error::<T, I>::Frozen);
 		with_details(&class_details, &mut details)?;
 
@@ -92,7 +93,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		maybe_check_owner: Option<T::AccountId>,
 	) -> Result<DestroyWitness, DispatchError> {
 		Class::<T, I>::try_mutate_exists(class, |maybe_details| {
-			let class_details = maybe_details.take().ok_or(Error::<T, I>::Unknown)?;
+			let class_details = maybe_details.take().ok_or(Error::<T, I>::UnknownClass)?;
 			if let Some(check_owner) = maybe_check_owner {
 				ensure!(class_details.owner == check_owner, Error::<T, I>::NoPermission);
 			}
@@ -131,7 +132,7 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		ensure!(!Asset::<T, I>::contains_key(class, instance), Error::<T, I>::AlreadyExists);
 
 		Class::<T, I>::try_mutate(&class, |maybe_class_details| -> DispatchResult {
-			let class_details = maybe_class_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+			let class_details = maybe_class_details.as_mut().ok_or(Error::<T, I>::UnknownClass)?;
 
 			with_details(&class_details)?;
 
@@ -165,9 +166,10 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 		let owner = Class::<T, I>::try_mutate(
 			&class,
 			|maybe_class_details| -> Result<T::AccountId, DispatchError> {
-				let class_details = maybe_class_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+				let class_details =
+					maybe_class_details.as_mut().ok_or(Error::<T, I>::UnknownClass)?;
 				let details =
-					Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
+					Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::UnknownClass)?;
 				with_details(&class_details, &details)?;
 
 				// Return the deposit.
diff --git a/substrate/frame/uniques/src/lib.rs b/substrate/frame/uniques/src/lib.rs
index 2956735e5e..f35bb3fd61 100644
--- a/substrate/frame/uniques/src/lib.rs
+++ b/substrate/frame/uniques/src/lib.rs
@@ -303,7 +303,7 @@ pub mod pallet {
 		/// The signing account has no permission to do the operation.
 		NoPermission,
 		/// The given asset ID is unknown.
-		Unknown,
+		UnknownClass,
 		/// The asset instance ID has already been used for an asset.
 		AlreadyExists,
 		/// The owner turned out to be different to what was expected.
@@ -561,7 +561,8 @@ pub mod pallet {
 		) -> DispatchResult {
 			let origin = ensure_signed(origin)?;
 
-			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let mut class_details =
+				Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			ensure!(class_details.owner == origin, Error::<T, I>::NoPermission);
 			let deposit = match class_details.free_holding {
 				true => Zero::zero(),
@@ -621,8 +622,8 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 
 			let mut details =
-				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
-			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::UnknownClass)?;
+			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			ensure!(class_details.freezer == origin, Error::<T, I>::NoPermission);
 
 			details.is_frozen = true;
@@ -651,8 +652,8 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 
 			let mut details =
-				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
-			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::UnknownClass)?;
+			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			ensure!(class_details.admin == origin, Error::<T, I>::NoPermission);
 
 			details.is_frozen = false;
@@ -679,7 +680,7 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 
 			Class::<T, I>::try_mutate(class, |maybe_details| {
-				let details = maybe_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+				let details = maybe_details.as_mut().ok_or(Error::<T, I>::UnknownClass)?;
 				ensure!(&origin == &details.freezer, Error::<T, I>::NoPermission);
 
 				details.is_frozen = true;
@@ -706,7 +707,7 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 
 			Class::<T, I>::try_mutate(class, |maybe_details| {
-				let details = maybe_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+				let details = maybe_details.as_mut().ok_or(Error::<T, I>::UnknownClass)?;
 				ensure!(&origin == &details.admin, Error::<T, I>::NoPermission);
 
 				details.is_frozen = false;
@@ -736,7 +737,7 @@ pub mod pallet {
 			let owner = T::Lookup::lookup(owner)?;
 
 			Class::<T, I>::try_mutate(class, |maybe_details| {
-				let details = maybe_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+				let details = maybe_details.as_mut().ok_or(Error::<T, I>::UnknownClass)?;
 				ensure!(&origin == &details.owner, Error::<T, I>::NoPermission);
 				if details.owner == owner {
 					return Ok(())
@@ -784,7 +785,7 @@ pub mod pallet {
 			let freezer = T::Lookup::lookup(freezer)?;
 
 			Class::<T, I>::try_mutate(class, |maybe_details| {
-				let details = maybe_details.as_mut().ok_or(Error::<T, I>::Unknown)?;
+				let details = maybe_details.as_mut().ok_or(Error::<T, I>::UnknownClass)?;
 				ensure!(&origin == &details.owner, Error::<T, I>::NoPermission);
 
 				details.issuer = issuer.clone();
@@ -820,9 +821,9 @@ pub mod pallet {
 
 			let delegate = T::Lookup::lookup(delegate)?;
 
-			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			let mut details =
-				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
+				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::UnknownClass)?;
 
 			if let Some(check) = maybe_check {
 				let permitted = &check == &class_details.admin || &check == &details.owner;
@@ -870,9 +871,9 @@ pub mod pallet {
 				.map(|_| None)
 				.or_else(|origin| ensure_signed(origin).map(Some).map_err(DispatchError::from))?;
 
-			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			let mut details =
-				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::Unknown)?;
+				Asset::<T, I>::get(&class, &instance).ok_or(Error::<T, I>::UnknownClass)?;
 			if let Some(check) = maybe_check {
 				let permitted = &check == &class_details.admin || &check == &details.owner;
 				ensure!(permitted, Error::<T, I>::NoPermission);
@@ -925,7 +926,7 @@ pub mod pallet {
 			T::ForceOrigin::ensure_origin(origin)?;
 
 			Class::<T, I>::try_mutate(class, |maybe_asset| {
-				let mut asset = maybe_asset.take().ok_or(Error::<T, I>::Unknown)?;
+				let mut asset = maybe_asset.take().ok_or(Error::<T, I>::UnknownClass)?;
 				let old_owner = asset.owner;
 				let new_owner = T::Lookup::lookup(owner)?;
 				asset.owner = new_owner.clone();
@@ -972,7 +973,8 @@ pub mod pallet {
 				.map(|_| None)
 				.or_else(|origin| ensure_signed(origin).map(Some))?;
 
-			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let mut class_details =
+				Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			if let Some(check_owner) = &maybe_check_owner {
 				ensure!(check_owner == &class_details.owner, Error::<T, I>::NoPermission);
 			}
@@ -1033,7 +1035,8 @@ pub mod pallet {
 				.map(|_| None)
 				.or_else(|origin| ensure_signed(origin).map(Some))?;
 
-			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let mut class_details =
+				Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			if let Some(check_owner) = &maybe_check_owner {
 				ensure!(check_owner == &class_details.owner, Error::<T, I>::NoPermission);
 			}
@@ -1083,7 +1086,8 @@ pub mod pallet {
 				.map(|_| None)
 				.or_else(|origin| ensure_signed(origin).map(Some))?;
 
-			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let mut class_details =
+				Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 
 			if let Some(check_owner) = &maybe_check_owner {
 				ensure!(check_owner == &class_details.owner, Error::<T, I>::NoPermission);
@@ -1142,7 +1146,8 @@ pub mod pallet {
 				.map(|_| None)
 				.or_else(|origin| ensure_signed(origin).map(Some))?;
 
-			let mut class_details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let mut class_details =
+				Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			if let Some(check_owner) = &maybe_check_owner {
 				ensure!(check_owner == &class_details.owner, Error::<T, I>::NoPermission);
 			}
@@ -1154,7 +1159,7 @@ pub mod pallet {
 				if metadata.is_some() {
 					class_details.instance_metadatas.saturating_dec();
 				}
-				let deposit = metadata.take().ok_or(Error::<T, I>::Unknown)?.deposit;
+				let deposit = metadata.take().ok_or(Error::<T, I>::UnknownClass)?.deposit;
 				T::Currency::unreserve(&class_details.owner, deposit);
 				class_details.total_deposit.saturating_reduce(deposit);
 
@@ -1191,7 +1196,7 @@ pub mod pallet {
 				.map(|_| None)
 				.or_else(|origin| ensure_signed(origin).map(Some))?;
 
-			let mut details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let mut details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			if let Some(check_owner) = &maybe_check_owner {
 				ensure!(check_owner == &details.owner, Error::<T, I>::NoPermission);
 			}
@@ -1245,7 +1250,7 @@ pub mod pallet {
 				.map(|_| None)
 				.or_else(|origin| ensure_signed(origin).map(Some))?;
 
-			let details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::Unknown)?;
+			let details = Class::<T, I>::get(&class).ok_or(Error::<T, I>::UnknownClass)?;
 			if let Some(check_owner) = &maybe_check_owner {
 				ensure!(check_owner == &details.owner, Error::<T, I>::NoPermission);
 			}
@@ -1254,7 +1259,7 @@ pub mod pallet {
 				let was_frozen = metadata.as_ref().map_or(false, |m| m.is_frozen);
 				ensure!(maybe_check_owner.is_none() || !was_frozen, Error::<T, I>::Frozen);
 
-				let deposit = metadata.take().ok_or(Error::<T, I>::Unknown)?.deposit;
+				let deposit = metadata.take().ok_or(Error::<T, I>::UnknownClass)?.deposit;
 				T::Currency::unreserve(&details.owner, deposit);
 				Self::deposit_event(Event::ClassMetadataCleared { class });
 				Ok(())
diff --git a/substrate/frame/uniques/src/tests.rs b/substrate/frame/uniques/src/tests.rs
index 293140d5ed..12f39c78bf 100644
--- a/substrate/frame/uniques/src/tests.rs
+++ b/substrate/frame/uniques/src/tests.rs
@@ -263,7 +263,7 @@ fn set_class_metadata_should_work() {
 		// Cannot add metadata to unknown asset
 		assert_noop!(
 			Uniques::set_class_metadata(Origin::signed(1), 0, bvec![0u8; 20], false),
-			Error::<Test>::Unknown,
+			Error::<Test>::UnknownClass,
 		);
 		assert_ok!(Uniques::force_create(Origin::root(), 0, 1, false));
 		// Cannot add metadata to unowned asset
@@ -307,7 +307,10 @@ fn set_class_metadata_should_work() {
 			Uniques::clear_class_metadata(Origin::signed(2), 0),
 			Error::<Test>::NoPermission
 		);
-		assert_noop!(Uniques::clear_class_metadata(Origin::signed(1), 1), Error::<Test>::Unknown);
+		assert_noop!(
+			Uniques::clear_class_metadata(Origin::signed(1), 1),
+			Error::<Test>::UnknownClass
+		);
 		assert_ok!(Uniques::clear_class_metadata(Origin::signed(1), 0));
 		assert!(!ClassMetadataOf::<Test>::contains_key(0));
 	});
@@ -361,7 +364,10 @@ fn set_instance_metadata_should_work() {
 			Uniques::clear_metadata(Origin::signed(2), 0, 42),
 			Error::<Test>::NoPermission
 		);
-		assert_noop!(Uniques::clear_metadata(Origin::signed(1), 1, 42), Error::<Test>::Unknown);
+		assert_noop!(
+			Uniques::clear_metadata(Origin::signed(1), 1, 42),
+			Error::<Test>::UnknownClass
+		);
 		assert_ok!(Uniques::clear_metadata(Origin::signed(1), 0, 42));
 		assert!(!InstanceMetadataOf::<Test>::contains_key(0, 42));
 	});
@@ -486,7 +492,7 @@ fn burn_works() {
 		assert_ok!(Uniques::force_create(Origin::root(), 0, 1, false));
 		assert_ok!(Uniques::set_team(Origin::signed(1), 0, 2, 3, 4));
 
-		assert_noop!(Uniques::burn(Origin::signed(5), 0, 42, Some(5)), Error::<Test>::Unknown);
+		assert_noop!(Uniques::burn(Origin::signed(5), 0, 42, Some(5)), Error::<Test>::UnknownClass);
 
 		assert_ok!(Uniques::mint(Origin::signed(2), 0, 42, 5));
 		assert_ok!(Uniques::mint(Origin::signed(2), 0, 69, 5));
@@ -525,11 +531,11 @@ fn cancel_approval_works() {
 		assert_ok!(Uniques::approve_transfer(Origin::signed(2), 0, 42, 3));
 		assert_noop!(
 			Uniques::cancel_approval(Origin::signed(2), 1, 42, None),
-			Error::<Test>::Unknown
+			Error::<Test>::UnknownClass
 		);
 		assert_noop!(
 			Uniques::cancel_approval(Origin::signed(2), 0, 43, None),
-			Error::<Test>::Unknown
+			Error::<Test>::UnknownClass
 		);
 		assert_noop!(
 			Uniques::cancel_approval(Origin::signed(3), 0, 42, None),
@@ -557,11 +563,11 @@ fn cancel_approval_works_with_admin() {
 		assert_ok!(Uniques::approve_transfer(Origin::signed(2), 0, 42, 3));
 		assert_noop!(
 			Uniques::cancel_approval(Origin::signed(1), 1, 42, None),
-			Error::<Test>::Unknown
+			Error::<Test>::UnknownClass
 		);
 		assert_noop!(
 			Uniques::cancel_approval(Origin::signed(1), 0, 43, None),
-			Error::<Test>::Unknown
+			Error::<Test>::UnknownClass
 		);
 		assert_noop!(
 			Uniques::cancel_approval(Origin::signed(1), 0, 42, Some(4)),
@@ -583,8 +589,14 @@ fn cancel_approval_works_with_force() {
 		assert_ok!(Uniques::mint(Origin::signed(1), 0, 42, 2));
 
 		assert_ok!(Uniques::approve_transfer(Origin::signed(2), 0, 42, 3));
-		assert_noop!(Uniques::cancel_approval(Origin::root(), 1, 42, None), Error::<Test>::Unknown);
-		assert_noop!(Uniques::cancel_approval(Origin::root(), 0, 43, None), Error::<Test>::Unknown);
+		assert_noop!(
+			Uniques::cancel_approval(Origin::root(), 1, 42, None),
+			Error::<Test>::UnknownClass
+		);
+		assert_noop!(
+			Uniques::cancel_approval(Origin::root(), 0, 43, None),
+			Error::<Test>::UnknownClass
+		);
 		assert_noop!(
 			Uniques::cancel_approval(Origin::root(), 0, 42, Some(4)),
 			Error::<Test>::WrongDelegate