diff --git a/polkadot/node/core/av-store/src/tests.rs b/polkadot/node/core/av-store/src/tests.rs
index 4e83e3d7f7..330e0c529a 100644
--- a/polkadot/node/core/av-store/src/tests.rs
+++ b/polkadot/node/core/av-store/src/tests.rs
@@ -74,6 +74,7 @@ impl Default for TestState {
 			hrmp_mqc_heads: Vec::new(),
 			dmq_mqc_head: Default::default(),
 			max_pov_size: 1024,
+			relay_storage_root: Default::default(),
 		};
 
 		let pruning_config = PruningConfig {
diff --git a/polkadot/node/core/backing/src/lib.rs b/polkadot/node/core/backing/src/lib.rs
index 841ea69670..8ac7df309f 100644
--- a/polkadot/node/core/backing/src/lib.rs
+++ b/polkadot/node/core/backing/src/lib.rs
@@ -1250,6 +1250,7 @@ mod tests {
 					hrmp_mqc_heads: Vec::new(),
 					dmq_mqc_head: Default::default(),
 					max_pov_size: 1024,
+					relay_storage_root: Default::default(),
 				},
 				transient: TransientValidationData {
 					max_code_size: 1000,
diff --git a/polkadot/node/core/proposer/src/lib.rs b/polkadot/node/core/proposer/src/lib.rs
index 96eb6bb95f..3e1e2919f7 100644
--- a/polkadot/node/core/proposer/src/lib.rs
+++ b/polkadot/node/core/proposer/src/lib.rs
@@ -98,11 +98,13 @@ where
 		// data to be moved into the future
 		let overseer = self.overseer.clone();
 		let parent_header_hash = parent_header.hash();
+		let parent_header = parent_header.clone();
 
 		async move {
 			Ok(Proposer {
 				inner: proposer?,
 				overseer,
+				parent_header,
 				parent_header_hash,
 			})
 		}.boxed()
@@ -116,6 +118,7 @@ where
 pub struct Proposer<TxPool: TransactionPool<Block = Block>, Backend, Client> {
 	inner: sc_basic_authorship::Proposer<Backend, Block, Client, TxPool>,
 	overseer: OverseerHandler,
+	parent_header: Header,
 	parent_header_hash: Hash,
 }
 
@@ -209,9 +212,14 @@ where
 
 			drop(_span);
 
+			let inclusion_inherent_data = (
+				provisioner_data.0,
+				provisioner_data.1,
+				self.parent_header,
+			);
 			inherent_data.put_data(
 				polkadot_primitives::v1::INCLUSION_INHERENT_IDENTIFIER,
-				&provisioner_data,
+				&inclusion_inherent_data,
 			)?;
 
 			let _span = span.child("authorship-propose");
diff --git a/polkadot/node/network/availability-distribution/src/tests.rs b/polkadot/node/network/availability-distribution/src/tests.rs
index a34caec7ab..d06a98402d 100644
--- a/polkadot/node/network/availability-distribution/src/tests.rs
+++ b/polkadot/node/network/availability-distribution/src/tests.rs
@@ -192,6 +192,7 @@ impl Default for TestState {
 			hrmp_mqc_heads: Vec::new(),
 			dmq_mqc_head: Default::default(),
 			max_pov_size: 1024,
+			relay_storage_root: Default::default(),
 		};
 
 		let pov_block_a = PoV {
diff --git a/polkadot/node/test/client/src/block_builder.rs b/polkadot/node/test/client/src/block_builder.rs
index de49ae4886..f9848a3064 100644
--- a/polkadot/node/test/client/src/block_builder.rs
+++ b/polkadot/node/test/client/src/block_builder.rs
@@ -71,10 +71,19 @@ impl InitPolkadotBlockBuilder for Client {
 			.put_data(sp_timestamp::INHERENT_IDENTIFIER, &timestamp)
 			.expect("Put timestamp inherent data");
 
+		let parent_header = self.header(at)
+			.expect("Get the parent block header")
+			.expect("The target block header must exist");
+		let provisioner_data = polkadot_node_subsystem::messages::ProvisionerInherentData::default();
+		let inclusion_inherent_data = (
+			provisioner_data.0,
+			provisioner_data.1,
+			parent_header,
+		);
 		inherent_data
 			.put_data(
 				polkadot_primitives::v1::INCLUSION_INHERENT_IDENTIFIER,
-				&polkadot_node_subsystem::messages::ProvisionerInherentData::default(),
+				&inclusion_inherent_data,
 			)
 			.expect("Put inclusion inherent data");
 
diff --git a/polkadot/primitives/src/v1.rs b/polkadot/primitives/src/v1.rs
index a9666fe793..6104d6aae2 100644
--- a/polkadot/primitives/src/v1.rs
+++ b/polkadot/primitives/src/v1.rs
@@ -284,6 +284,8 @@ pub struct PersistedValidationData<N = BlockNumber> {
 	pub parent_head: HeadData,
 	/// The relay-chain block number this is in the context of.
 	pub block_number: N,
+	/// The relay-chain block storage root this is in the context of.
+	pub relay_storage_root: Hash,
 	/// The list of MQC heads for the inbound channels paired with the sender para ids. This
 	/// vector is sorted ascending by the para id and doesn't contain multiple entries with the same
 	/// sender.
diff --git a/polkadot/roadmap/implementers-guide/src/runtime/inclusion.md b/polkadot/roadmap/implementers-guide/src/runtime/inclusion.md
index 9a6228a8c1..5cabb109dd 100644
--- a/polkadot/roadmap/implementers-guide/src/runtime/inclusion.md
+++ b/polkadot/roadmap/implementers-guide/src/runtime/inclusion.md
@@ -59,7 +59,7 @@ All failed checks should lead to an unrecoverable error making the block invalid
   1. For each applied bit of each availability-bitfield, set the bit for the validator in the `CandidatePendingAvailability`'s `availability_votes` bitfield. Track all candidates that now have >2/3 of bits set in their `availability_votes`. These candidates are now available and can be enacted.
   1. For all now-available candidates, invoke the `enact_candidate` routine with the candidate and relay-parent number.
   1. Return a list of freed cores consisting of the cores where candidates have become available.
-* `process_candidates(BackedCandidates, scheduled: Vec<CoreAssignment>, group_validators: Fn(GroupIndex) -> Option<Vec<ValidatorIndex>>)`:
+* `process_candidates(parent_storage_root, BackedCandidates, scheduled: Vec<CoreAssignment>, group_validators: Fn(GroupIndex) -> Option<Vec<ValidatorIndex>>)`:
   1. check that each candidate corresponds to a scheduled core and that they are ordered in the same order the cores appear in assignments in `scheduled`.
   1. check that `scheduled` is sorted ascending by `CoreIndex`, without duplicates.
   1. check that there is no candidate pending availability for any scheduled `ParaId`.
diff --git a/polkadot/roadmap/implementers-guide/src/runtime/inclusioninherent.md b/polkadot/roadmap/implementers-guide/src/runtime/inclusioninherent.md
index 54ebf3af7b..3f23989642 100644
--- a/polkadot/roadmap/implementers-guide/src/runtime/inclusioninherent.md
+++ b/polkadot/roadmap/implementers-guide/src/runtime/inclusioninherent.md
@@ -16,11 +16,13 @@ Included: Option<()>,
 
 ## Entry Points
 
-* `inclusion`: This entry-point accepts two parameters: [`Bitfields`](../types/availability.md#signed-availability-bitfield) and [`BackedCandidates`](../types/backing.md#backed-candidate).
+* `inclusion`: This entry-point accepts three parameters: The relay-chain parent block header, [`Bitfields`](../types/availability.md#signed-availability-bitfield) and [`BackedCandidates`](../types/backing.md#backed-candidate).
+    1. Hash the parent header and make sure that it corresponds to the block hash of the parent (tracked by the `frame_system` FRAME module),
     1. The `Bitfields` are first forwarded to the `Inclusion::process_bitfields` routine, returning a set of freed cores. Provide a `Scheduler::core_para` as a core-lookup to the `process_bitfields` routine. Annotate each of these freed cores with `FreedReason::Concluded`.
     1. If `Scheduler::availability_timeout_predicate` is `Some`, invoke `Inclusion::collect_pending` using it, and add timed-out cores to the free cores, annotated with `FreedReason::TimedOut`.
     1. Invoke `Scheduler::schedule(freed)`
-	1. Invoke the `Inclusion::process_candidates` routine with the parameters `(backed_candidates, Scheduler::scheduled(), Scheduler::group_validators)`.
+    1. Extract `parent_storage_root` from the parent header,
+    1. Invoke the `Inclusion::process_candidates` routine with the parameters `(parent_storage_root, backed_candidates, Scheduler::scheduled(), Scheduler::group_validators)`.
     1. Call `Scheduler::occupied` using the return value of the `Inclusion::process_candidates` call above, first sorting the list of assigned core indices.
     1. Call the `Ump::process_pending_upward_messages` routine to execute all messages in upward dispatch queues.
     1. If all of the above succeeds, set `Included` to `Some(())`.
diff --git a/polkadot/roadmap/implementers-guide/src/types/candidate.md b/polkadot/roadmap/implementers-guide/src/types/candidate.md
index 86c80153f3..c9da4b683f 100644
--- a/polkadot/roadmap/implementers-guide/src/types/candidate.md
+++ b/polkadot/roadmap/implementers-guide/src/types/candidate.md
@@ -127,6 +127,8 @@ struct PersistedValidationData {
 	parent_head: HeadData,
 	/// The relay-chain block number this is in the context of. This informs the collator.
 	block_number: BlockNumber,
+	/// The relay-chain block storage root this is in the context of.
+	relay_storage_root: Hash,
 	/// The MQC head for the DMQ.
 	///
 	/// The DMQ MQC head will be used by the validation function to authorize the downward messages
diff --git a/polkadot/runtime/parachains/src/inclusion.rs b/polkadot/runtime/parachains/src/inclusion.rs
index 95481b57a0..4f0466f788 100644
--- a/polkadot/runtime/parachains/src/inclusion.rs
+++ b/polkadot/runtime/parachains/src/inclusion.rs
@@ -25,7 +25,7 @@ use primitives::v1::{
 	ValidatorId, CandidateCommitments, CandidateDescriptor, ValidatorIndex, Id as ParaId,
 	AvailabilityBitfield as AvailabilityBitfield, SignedAvailabilityBitfields, SigningContext,
 	BackedCandidate, CoreIndex, GroupIndex, CommittedCandidateReceipt,
-	CandidateReceipt, HeadData, CandidateHash,
+	CandidateReceipt, HeadData, CandidateHash, Hash,
 };
 use frame_support::{
 	decl_storage, decl_module, decl_error, decl_event, ensure, debug,
@@ -382,11 +382,13 @@ impl<T: Config> Module<T> {
 		Ok(freed_cores)
 	}
 
-	/// Process candidates that have been backed. Provide a set of candidates and scheduled cores.
+	/// Process candidates that have been backed. Provide the relay storage root, a set of candidates
+	/// and scheduled cores.
 	///
 	/// Both should be sorted ascending by core index, and the candidates should be a subset of
 	/// scheduled cores. If these conditions are not met, the execution of the function fails.
 	pub(crate) fn process_candidates(
+		parent_storage_root: Hash,
 		candidates: Vec<BackedCandidate<T::Hash>>,
 		scheduled: Vec<CoreAssignment>,
 		group_validators: impl Fn(GroupIndex) -> Option<Vec<ValidatorIndex>>,
@@ -491,6 +493,7 @@ impl<T: Config> Module<T> {
 								match crate::util::make_persisted_validation_data::<T>(
 									para_id,
 									relay_parent_number,
+									parent_storage_root,
 								) {
 									Some(l) => l,
 									None => {
@@ -1129,6 +1132,7 @@ mod tests {
 			= crate::util::make_persisted_validation_data::<Test>(
 				para_id,
 				relay_parent_number,
+				Default::default(),
 			)?;
 		Some(persisted_validation_data.hash())
 	}
@@ -1634,6 +1638,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![chain_b_assignment.clone()],
 						&group_validators,
@@ -1692,6 +1697,7 @@ mod tests {
 				// out-of-order manifests as unscheduled.
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed_b, backed_a],
 						vec![chain_a_assignment.clone(), chain_b_assignment.clone()],
 						&group_validators,
@@ -1726,6 +1732,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![chain_a_assignment.clone()],
 						&group_validators,
@@ -1762,6 +1769,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![chain_a_assignment.clone()],
 						&group_validators,
@@ -1798,6 +1806,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![
 							chain_a_assignment.clone(),
@@ -1841,6 +1850,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![thread_a_assignment.clone()],
 						&group_validators,
@@ -1888,6 +1898,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![chain_a_assignment.clone()],
 						&group_validators,
@@ -1929,6 +1940,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![chain_a_assignment.clone()],
 						&group_validators,
@@ -1975,6 +1987,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![chain_a_assignment.clone()],
 						&group_validators,
@@ -2010,6 +2023,7 @@ mod tests {
 
 				assert_eq!(
 					Inclusion::process_candidates(
+						Default::default(),
 						vec![backed],
 						vec![chain_a_assignment.clone()],
 						&group_validators,
@@ -2151,6 +2165,7 @@ mod tests {
 			));
 
 			let occupied_cores = Inclusion::process_candidates(
+				Default::default(),
 				vec![backed_a, backed_b, backed_c],
 				vec![
 					chain_a_assignment.clone(),
@@ -2283,6 +2298,7 @@ mod tests {
 			));
 
 			let occupied_cores = Inclusion::process_candidates(
+				Default::default(),
 				vec![backed_a],
 				vec![
 					chain_a_assignment.clone(),
diff --git a/polkadot/runtime/parachains/src/inclusion_inherent.rs b/polkadot/runtime/parachains/src/inclusion_inherent.rs
index bb25f5c80f..27a319dced 100644
--- a/polkadot/runtime/parachains/src/inclusion_inherent.rs
+++ b/polkadot/runtime/parachains/src/inclusion_inherent.rs
@@ -23,8 +23,9 @@
 
 use sp_std::prelude::*;
 use primitives::v1::{
-	BackedCandidate, SignedAvailabilityBitfields, INCLUSION_INHERENT_IDENTIFIER,
+	BackedCandidate, SignedAvailabilityBitfields, INCLUSION_INHERENT_IDENTIFIER, Header,
 };
+use sp_runtime::traits::One;
 use frame_support::{
 	decl_error, decl_module, decl_storage, ensure,
 	dispatch::DispatchResult,
@@ -57,6 +58,9 @@ decl_error! {
 	pub enum Error for Module<T: Config> {
 		/// Inclusion inherent called more than once per block.
 		TooManyInclusionInherents,
+		/// The hash of the submitted parent header doesn't correspond to the saved block hash of
+		/// the parent.
+		InvalidParentHeader,
 	}
 }
 
@@ -81,10 +85,19 @@ decl_module! {
 			origin,
 			signed_bitfields: SignedAvailabilityBitfields,
 			backed_candidates: Vec<BackedCandidate<T::Hash>>,
+			parent_header: Header,
 		) -> DispatchResult {
 			ensure_none(origin)?;
 			ensure!(!<Included>::exists(), Error::<T>::TooManyInclusionInherents);
 
+			// Check that the submitted parent header indeed corresponds to the previous block hash.
+			let now = <frame_system::Module<T>>::block_number();
+			let parent_hash = <frame_system::Module<T>>::block_hash(now - One::one());
+			ensure!(
+				parent_header.hash().as_ref() == parent_hash.as_ref(),
+				Error::<T>::InvalidParentHeader,
+			);
+
 			// Process new availability bitfields, yielding any availability cores whose
 			// work has now concluded.
 			let freed_concluded = <inclusion::Module<T>>::process_bitfields(
@@ -107,7 +120,9 @@ decl_module! {
 			<scheduler::Module<T>>::schedule(freed);
 
 			// Process backed candidates according to scheduled cores.
+			let parent_storage_root = parent_header.state_root;
 			let occupied = <inclusion::Module<T>>::process_candidates(
+				parent_storage_root,
 				backed_candidates,
 				<scheduler::Module<T>>::scheduled(),
 				<scheduler::Module<T>>::group_validators,
@@ -135,14 +150,27 @@ impl<T: Config> ProvideInherent for Module<T> {
 	fn create_inherent(data: &InherentData) -> Option<Self::Call> {
 		data.get_data(&Self::INHERENT_IDENTIFIER)
 			.expect("inclusion inherent data failed to decode")
-			.map(|(signed_bitfields, backed_candidates): (SignedAvailabilityBitfields, Vec<BackedCandidate<T::Hash>>)| {
-				// Sanity check: session changes can invalidate an inherent, and we _really_ don't want that to happen.
-				// See github.com/paritytech/polkadot/issues/1327
-				if Self::inclusion(frame_system::RawOrigin::None.into(), signed_bitfields.clone(), backed_candidates.clone()).is_ok() {
-					Call::inclusion(signed_bitfields, backed_candidates)
-				} else {
-					Call::inclusion(Vec::new().into(), Vec::new())
+			.map(
+				|(signed_bitfields, backed_candidates, parent_header): (
+					SignedAvailabilityBitfields,
+					Vec<BackedCandidate<T::Hash>>,
+					Header,
+				)| {
+					// Sanity check: session changes can invalidate an inherent, and we _really_ don't want that to happen.
+					// See github.com/paritytech/polkadot/issues/1327
+					if Self::inclusion(
+						frame_system::RawOrigin::None.into(),
+						signed_bitfields.clone(),
+						backed_candidates.clone(),
+						parent_header.clone(),
+					)
+					.is_ok()
+					{
+						Call::inclusion(signed_bitfields, backed_candidates, parent_header)
+					} else {
+						Call::inclusion(Vec::new().into(), Vec::new(), parent_header)
+					}
 				}
-			})
+			)
 	}
 }
diff --git a/polkadot/runtime/parachains/src/runtime_api_impl/v1.rs b/polkadot/runtime/parachains/src/runtime_api_impl/v1.rs
index d3ef7a1ee3..46503d2977 100644
--- a/polkadot/runtime/parachains/src/runtime_api_impl/v1.rs
+++ b/polkadot/runtime/parachains/src/runtime_api_impl/v1.rs
@@ -24,7 +24,7 @@ use primitives::v1::{
 	Id as ParaId, OccupiedCoreAssumption, SessionIndex, ValidationCode,
 	CommittedCandidateReceipt, ScheduledCore, OccupiedCore, CoreOccupied, CoreIndex,
 	GroupIndex, CandidateEvent, PersistedValidationData, SessionInfo,
-	InboundDownwardMessage, InboundHrmpMessage,
+	InboundDownwardMessage, InboundHrmpMessage, Hash,
 };
 use frame_support::debug;
 use crate::{initializer, inclusion, scheduler, configuration, paras, session_info, dmp, hrmp};
@@ -190,18 +190,24 @@ fn with_assumption<Config, T, F>(
 pub fn full_validation_data<T: initializer::Config>(
 	para_id: ParaId,
 	assumption: OccupiedCoreAssumption,
-)
-	-> Option<ValidationData<T::BlockNumber>>
-{
+) -> Option<ValidationData<T::BlockNumber>> {
+	use parity_scale_codec::Decode as _;
 	let relay_parent_number = <frame_system::Module<T>>::block_number();
-	with_assumption::<T, _, _>(
-		para_id,
-		assumption,
-		|| Some(ValidationData {
-			persisted: crate::util::make_persisted_validation_data::<T>(para_id, relay_parent_number)?,
-			transient: crate::util::make_transient_validation_data::<T>(para_id, relay_parent_number)?,
-		}),
-	)
+	let relay_storage_root = Hash::decode(&mut &sp_io::storage::root()[..])
+		.expect("storage root must decode to the Hash type; qed");
+	with_assumption::<T, _, _>(para_id, assumption, || {
+		Some(ValidationData {
+			persisted: crate::util::make_persisted_validation_data::<T>(
+				para_id,
+				relay_parent_number,
+				relay_storage_root,
+			)?,
+			transient: crate::util::make_transient_validation_data::<T>(
+				para_id,
+				relay_parent_number,
+			)?,
+		})
+	})
 }
 
 /// Implementation for the `persisted_validation_data` function of the runtime API.
@@ -209,12 +215,17 @@ pub fn persisted_validation_data<T: initializer::Config>(
 	para_id: ParaId,
 	assumption: OccupiedCoreAssumption,
 ) -> Option<PersistedValidationData<T::BlockNumber>> {
+	use parity_scale_codec::Decode as _;
 	let relay_parent_number = <frame_system::Module<T>>::block_number();
-	with_assumption::<T, _, _>(
-		para_id,
-		assumption,
-		|| crate::util::make_persisted_validation_data::<T>(para_id, relay_parent_number),
-	)
+	let relay_storage_root = Hash::decode(&mut &sp_io::storage::root()[..])
+		.expect("storage root must decode to the Hash type; qed");
+	with_assumption::<T, _, _>(para_id, assumption, || {
+		crate::util::make_persisted_validation_data::<T>(
+			para_id,
+			relay_parent_number,
+			relay_storage_root,
+		)
+	})
 }
 
 /// Implementation for the `check_validation_outputs` function of the runtime API.
diff --git a/polkadot/runtime/parachains/src/util.rs b/polkadot/runtime/parachains/src/util.rs
index d0f8913062..ce041981eb 100644
--- a/polkadot/runtime/parachains/src/util.rs
+++ b/polkadot/runtime/parachains/src/util.rs
@@ -18,22 +18,25 @@
 //! on all modules.
 
 use sp_runtime::traits::Saturating;
-use primitives::v1::{Id as ParaId, PersistedValidationData, TransientValidationData};
+use primitives::v1::{Id as ParaId, PersistedValidationData, TransientValidationData, Hash};
 
 use crate::{configuration, paras, dmp, hrmp};
 
-/// Make the persisted validation data for a particular parachain and a specified relay-parent.
+/// Make the persisted validation data for a particular parachain, a specified relay-parent and it's
+/// storage root.
 ///
 /// This ties together the storage of several modules.
 pub fn make_persisted_validation_data<T: paras::Config + hrmp::Config>(
 	para_id: ParaId,
 	relay_parent_number: T::BlockNumber,
+	relay_storage_root: Hash,
 ) -> Option<PersistedValidationData<T::BlockNumber>> {
 	let config = <configuration::Module<T>>::config();
 
 	Some(PersistedValidationData {
 		parent_head: <paras::Module<T>>::para_head(&para_id)?,
 		block_number: relay_parent_number,
+		relay_storage_root,
 		hrmp_mqc_heads: <hrmp::Module<T>>::hrmp_mqc_heads(para_id),
 		dmq_mqc_head: <dmp::Module<T>>::dmq_mqc_head(para_id),
 		max_pov_size: config.max_pov_size,
diff --git a/polkadot/runtime/rococo/src/lib.rs b/polkadot/runtime/rococo/src/lib.rs
index 05b5b92b8d..d5dc73a7ce 100644
--- a/polkadot/runtime/rococo/src/lib.rs
+++ b/polkadot/runtime/rococo/src/lib.rs
@@ -105,7 +105,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	spec_name: create_runtime_str!("rococo"),
 	impl_name: create_runtime_str!("parity-rococo-v1"),
 	authoring_version: 0,
-	spec_version: 12,
+	spec_version: 13,
 	impl_version: 0,
 	#[cfg(not(feature = "disable-runtime-api"))]
 	apis: RUNTIME_API_VERSIONS,