diff --git a/polkadot/runtime/parachains/src/inclusion/mod.rs b/polkadot/runtime/parachains/src/inclusion/mod.rs
index 683ebb61e404..79029952e7c1 100644
--- a/polkadot/runtime/parachains/src/inclusion/mod.rs
+++ b/polkadot/runtime/parachains/src/inclusion/mod.rs
@@ -443,6 +443,8 @@ pub(crate) enum UmpAcceptanceCheckErr {
 	/// The allowed number of `UMPSignal` messages in the queue was exceeded.
 	/// Currenly only one such message is allowed.
 	TooManyUMPSignals { count: u32 },
+	/// The UMP queue contains an invalid `UMPSignal`
+	InvalidUMPSignal,
 }
 
 impl fmt::Debug for UmpAcceptanceCheckErr {
@@ -472,7 +474,10 @@ impl fmt::Debug for UmpAcceptanceCheckErr {
 				write!(fmt, "upward message rejected because the para is off-boarding")
 			},
 			UmpAcceptanceCheckErr::TooManyUMPSignals { count } => {
-				write!(fmt, "the umpq queue has too many `UMPSignal` mesages ({} > 1 )", count)
+				write!(fmt, "the ump queue has too many `UMPSignal` mesages ({} > 1 )", count)
+			},
+			UmpAcceptanceCheckErr::InvalidUMPSignal => {
+				write!(fmt, "the ump queue contains an invalid UMP signal")
 			},
 		}
 	}
@@ -953,6 +958,10 @@ impl<T: Config> Pallet<T> {
 				})
 			}
 
+			if ump_signals.len() == 1 {
+				return Err(UmpAcceptanceCheckErr::InvalidUMPSignal)
+			}
+
 			upward_messages
 		} else {
 			upward_messages
diff --git a/polkadot/runtime/parachains/src/paras_inherent/tests.rs b/polkadot/runtime/parachains/src/paras_inherent/tests.rs
index e991890df954..f5c3d5077764 100644
--- a/polkadot/runtime/parachains/src/paras_inherent/tests.rs
+++ b/polkadot/runtime/parachains/src/paras_inherent/tests.rs
@@ -1742,6 +1742,73 @@ mod enter {
 		});
 	}
 
+	#[test]
+	fn invalid_ump_signals() {
+		let config = default_config();
+		assert!(config.configuration.config.scheduler_params.lookahead > 0);
+		new_test_ext(config).execute_with(|| {
+			// Set the elastic scaling MVP feature.
+			configuration::Pallet::<Test>::set_node_feature(
+				RuntimeOrigin::root(),
+				FeatureIndex::CandidateReceiptV2 as u8,
+				true,
+			)
+			.unwrap();
+
+			let mut backed_and_concluding = BTreeMap::new();
+			backed_and_concluding.insert(0, 1);
+			backed_and_concluding.insert(1, 1);
+			backed_and_concluding.insert(2, 1);
+
+			let unavailable_cores = vec![];
+
+			let scenario = make_inherent_data(TestConfig {
+				dispute_statements: BTreeMap::new(),
+				dispute_sessions: vec![], // No disputes
+				backed_and_concluding,
+				num_validators_per_core: 5,
+				code_upgrade: None,
+				fill_claimqueue: true,
+				elastic_paras: [(2, 8)].into_iter().collect(),
+				unavailable_cores: unavailable_cores.clone(),
+				v2_descriptor: true,
+				candidate_modifier: Some(|mut candidate: CommittedCandidateReceiptV2| {
+					if candidate.descriptor.para_id() == 1.into() {
+						// Drop the core selector to make it invalid
+						candidate
+							.commitments
+							.upward_messages
+							.truncate(candidate.commitments.upward_messages.len() - 1);
+					}
+					candidate
+				}),
+			});
+
+			let unfiltered_para_inherent_data = scenario.data.clone();
+
+			// Check the para inherent data is as expected:
+			// * 1 bitfield per validator (5 validators per core, 10 backed candidates)
+			assert_eq!(unfiltered_para_inherent_data.bitfields.len(), 50);
+			// * 10 v2 candidate descriptors.
+			assert_eq!(unfiltered_para_inherent_data.backed_candidates.len(), 10);
+
+			let mut inherent_data = InherentData::new();
+			inherent_data
+				.put_data(PARACHAINS_INHERENT_IDENTIFIER, &unfiltered_para_inherent_data)
+				.unwrap();
+
+			let dispatch_error = Pallet::<Test>::enter(
+				frame_system::RawOrigin::None.into(),
+				unfiltered_para_inherent_data,
+			)
+			.unwrap_err()
+			.error;
+
+			// We expect `enter` to fail because the inherent data contains backed candidates with
+			// v2 descriptors.
+			assert_eq!(dispatch_error, Error::<Test>::CandidatesFilteredDuringExecution.into());
+		});
+	}
 	#[test]
 	fn v2_descriptors_are_accepted() {
 		let config = default_config();
@@ -1937,7 +2004,7 @@ mod enter {
 		});
 	}
 
-	// A test to ensure that the `paras_inherent`` filters out candidates with invalid
+	// A test to ensure that the `paras_inherent` filters out candidates with invalid
 	// session index in the descriptor.
 	#[test]
 	fn invalid_session_index() {
diff --git a/polkadot/runtime/parachains/src/ump_tests.rs b/polkadot/runtime/parachains/src/ump_tests.rs
index 571fc5ab2271..d6cef850fb6a 100644
--- a/polkadot/runtime/parachains/src/ump_tests.rs
+++ b/polkadot/runtime/parachains/src/ump_tests.rs
@@ -164,7 +164,7 @@ mod check_upward_messages {
 			let max_per_candidate =
 				configuration::ActiveConfig::<Test>::get().max_upward_message_num_per_candidate;
 
-			for msg_size in 0..=max_size {
+			for msg_size in 1..=max_size {
 				check(P_0, vec![vec![0; msg_size as usize]], None);
 			}
 			for msg_size in max_size + 1..max_size + 10 {