diff --git a/Cargo.lock b/Cargo.lock
index dc5a35c2e8e1e..08803e885aa91 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2729,6 +2729,7 @@ dependencies = [
  "serde 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
  "substrate-codec 0.1.0",
+ "substrate-codec-derive 0.1.0",
  "substrate-primitives 0.1.0",
  "substrate-runtime-io 0.1.0",
  "substrate-runtime-primitives 0.1.0",
diff --git a/demo/runtime/src/lib.rs b/demo/runtime/src/lib.rs
index 69cf3536335b0..feee8626adb5f 100644
--- a/demo/runtime/src/lib.rs
+++ b/demo/runtime/src/lib.rs
@@ -53,10 +53,9 @@ extern crate substrate_runtime_timestamp as timestamp;
 extern crate substrate_runtime_version as version;
 extern crate demo_primitives;
 
-use rstd::prelude::*;
 use demo_primitives::{AccountId, AccountIndex, Balance, BlockNumber, Hash, Index, SessionKey, Signature};
 use runtime_primitives::generic;
-use runtime_primitives::traits::{Convert, BlakeTwo256};
+use runtime_primitives::traits::{Convert, BlakeTwo256, DigestItem};
 use version::RuntimeVersion;
 
 #[cfg(any(feature = "std", test))]
@@ -90,9 +89,9 @@ impl system::Trait for Runtime {
 	type BlockNumber = BlockNumber;
 	type Hash = Hash;
 	type Hashing = BlakeTwo256;
-	type Digest = generic::Digest<Vec<u8>>;
+	type Digest = generic::Digest<Log>;
 	type AccountId = AccountId;
-	type Header = generic::Header<BlockNumber, BlakeTwo256, Vec<u8>>;
+	type Header = generic::Header<BlockNumber, BlakeTwo256, Log>;
 	type Event = Event;
 }
 
@@ -112,6 +111,7 @@ pub type Balances = balances::Module<Runtime>;
 
 impl consensus::Trait for Runtime {
 	const NOTE_OFFLINE_POSITION: u32 = 1;
+	type Log = Log;
 	type SessionKey = SessionKey;
 	type OnOfflineValidator = Staking;
 }
@@ -173,6 +173,22 @@ impl_outer_event! {
 	}
 }
 
+impl_outer_log! {
+	pub enum Log for Runtime {
+		consensus
+	}
+}
+
+impl DigestItem for Log {
+	type AuthoritiesChange = consensus::AuthoritiesChange<SessionKey>;
+
+	fn as_authorities_change(&self) -> Option<&Self::AuthoritiesChange> {
+		match *self {
+			Log::consensus(ref item) => item.as_authorities_change(),
+		}
+	}
+}
+
 impl_outer_dispatch! {
 	#[derive(Clone, PartialEq, Eq)]
 	#[cfg_attr(feature = "std", derive(Debug, Serialize, Deserialize))]
@@ -203,7 +219,7 @@ impl_outer_dispatch! {
 /// The address format for describing accounts.
 pub type Address = balances::Address<Runtime>;
 /// Block header type as expected by this runtime.
-pub type Header = generic::Header<BlockNumber, BlakeTwo256, Vec<u8>>;
+pub type Header = generic::Header<BlockNumber, BlakeTwo256, Log>;
 /// Block type as expected by this runtime.
 pub type Block = generic::Block<Header, UncheckedExtrinsic>;
 /// BlockId type as expected by this runtime.
diff --git a/demo/runtime/wasm/Cargo.lock b/demo/runtime/wasm/Cargo.lock
index 38caaf9e7c531..5a7006c298ada 100644
--- a/demo/runtime/wasm/Cargo.lock
+++ b/demo/runtime/wasm/Cargo.lock
@@ -629,6 +629,7 @@ dependencies = [
  "serde 1.0.64 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.64 (registry+https://github.com/rust-lang/crates.io-index)",
  "substrate-codec 0.1.0",
+ "substrate-codec-derive 0.1.0",
  "substrate-primitives 0.1.0",
  "substrate-runtime-io 0.1.0",
  "substrate-runtime-primitives 0.1.0",
diff --git a/demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.compact.wasm b/demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.compact.wasm
index 9537c10de5fc7..1e64ab9760537 100644
Binary files a/demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.compact.wasm and b/demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.compact.wasm differ
diff --git a/demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.wasm b/demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.wasm
index 7f99674df3237..a7ed5f219890e 100755
Binary files a/demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.wasm and b/demo/runtime/wasm/target/wasm32-unknown-unknown/release/demo_runtime.wasm differ
diff --git a/substrate/executor/wasm/target/wasm32-unknown-unknown/release/runtime_test.compact.wasm b/substrate/executor/wasm/target/wasm32-unknown-unknown/release/runtime_test.compact.wasm
index 0ff8c1db3e8e2..75c6ebda9e7f2 100644
Binary files a/substrate/executor/wasm/target/wasm32-unknown-unknown/release/runtime_test.compact.wasm and b/substrate/executor/wasm/target/wasm32-unknown-unknown/release/runtime_test.compact.wasm differ
diff --git a/substrate/executor/wasm/target/wasm32-unknown-unknown/release/runtime_test.wasm b/substrate/executor/wasm/target/wasm32-unknown-unknown/release/runtime_test.wasm
index 15717f1d28d82..34d64bb11aca2 100755
Binary files a/substrate/executor/wasm/target/wasm32-unknown-unknown/release/runtime_test.wasm and b/substrate/executor/wasm/target/wasm32-unknown-unknown/release/runtime_test.wasm differ
diff --git a/substrate/runtime-support/src/lib.rs b/substrate/runtime-support/src/lib.rs
index ed22c6413e90d..54985efa25031 100644
--- a/substrate/runtime-support/src/lib.rs
+++ b/substrate/runtime-support/src/lib.rs
@@ -121,3 +121,27 @@ macro_rules! impl_outer_event {
 		)*
 	}
 }
+
+#[macro_export]
+macro_rules! impl_outer_log {
+
+	($(#[$attr:meta])* pub enum $name:ident for $trait:ident { $( $module:ident ),* }) => {
+		// Workaround for https://github.com/rust-lang/rust/issues/26925 . Remove when sorted.
+		#[derive(Clone, PartialEq, Eq, Encode, Decode)]
+		#[cfg_attr(feature = "std", derive(Debug, Serialize, Deserialize))]
+		$(#[$attr])*
+		#[allow(non_camel_case_types)]
+		pub enum $name {
+			$(
+				$module($module::Log<$trait>),
+			)*
+		}
+		$(
+			impl From<$module::Log<$trait>> for $name {
+				fn from(x: $module::Log<$trait>) -> Self {
+					$name::$module(x)
+				}
+			}
+		)*
+	};
+}
diff --git a/substrate/runtime/consensus/Cargo.toml b/substrate/runtime/consensus/Cargo.toml
index c9af11fc19683..dfdebbddc118f 100644
--- a/substrate/runtime/consensus/Cargo.toml
+++ b/substrate/runtime/consensus/Cargo.toml
@@ -8,6 +8,7 @@ hex-literal = "0.1.0"
 serde = { version = "1.0", default_features = false }
 serde_derive = { version = "1.0", optional = true }
 substrate-codec = { path = "../../codec", default_features = false }
+substrate-codec-derive = { path = "../../codec/derive", default_features = false }
 substrate-primitives = { path = "../../primitives", default_features = false }
 substrate-runtime-std = { path = "../../runtime-std", default_features = false }
 substrate-runtime-io = { path = "../../runtime-io", default_features = false }
@@ -21,6 +22,7 @@ std = [
 	"serde/std",
 	"serde_derive",
 	"substrate-codec/std",
+	"substrate-codec-derive/std",
 	"substrate-primitives/std",
 	"substrate-runtime-std/std",
 	"substrate-runtime-io/std",
diff --git a/substrate/runtime/consensus/src/lib.rs b/substrate/runtime/consensus/src/lib.rs
index df6d034c8f555..5aee25a71afac 100644
--- a/substrate/runtime/consensus/src/lib.rs
+++ b/substrate/runtime/consensus/src/lib.rs
@@ -32,6 +32,9 @@ extern crate serde;
 #[macro_use]
 extern crate serde_derive;
 
+#[macro_use]
+extern crate substrate_codec_derive;
+
 extern crate substrate_runtime_io as runtime_io;
 extern crate substrate_runtime_primitives as primitives;
 extern crate substrate_codec as codec;
@@ -41,8 +44,9 @@ extern crate substrate_primitives;
 use rstd::prelude::*;
 use runtime_support::{storage, Parameter};
 use runtime_support::dispatch::Result;
+use runtime_support::storage::StorageValue;
 use runtime_support::storage::unhashed::StorageVec;
-use primitives::traits::{MaybeSerializeDebug, MaybeEmpty};
+use primitives::traits::{MaybeSerializeDebug, MaybeEmpty, OnFinalise, Member, AuthoritiesChangeDigest};
 use primitives::bft::MisbehaviorReport;
 
 #[cfg(any(feature = "std", test))]
@@ -71,14 +75,71 @@ impl OnOfflineValidator for () {
 	fn on_offline_validator(_validator_index: usize) {}
 }
 
+pub type Log<T> = RawLog<
+	<T as Trait>::SessionKey,
+>;
+
+/// An logs in this module.
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
+#[derive(Encode, Decode, PartialEq, Eq, Clone)]
+pub enum RawLog<SessionKey> {
+	/// Authorities set has been changed. Contains the new set of authorities.
+	AuthoritiesChange(AuthoritiesChange<SessionKey>),
+}
+
+impl<SessionKey> RawLog<SessionKey> {
+	/// Try to cast the log entry as AuthoritiesChange log entry.
+	pub fn as_authorities_change(&self) -> Option<&AuthoritiesChange<SessionKey>> {
+		match *self {
+			RawLog::AuthoritiesChange(ref item) => Some(item),
+		}
+	}
+}
+
+/// Authorities change log entry.
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
+#[derive(Encode, Decode, PartialEq, Eq, Clone)]
+pub struct AuthoritiesChange<SessionKey> {
+	/// New set of authorities.
+	pub new_authorities: Vec<SessionKey>,
+}
+
+// Implementation for tests outside of this crate.
+impl<N> From<RawLog<N>> for u64 {
+	fn from(log: RawLog<N>) -> u64 {
+		match log {
+			RawLog::AuthoritiesChange(_) => 1,
+		}
+	}
+}
+
+impl<SessionKey: Member> AuthoritiesChangeDigest for AuthoritiesChange<SessionKey> {
+	type AuthorityId = SessionKey;
+
+	fn authorities(&self) -> &[Self::AuthorityId] {
+		&self.new_authorities
+	}
+}
+
 pub trait Trait: system::Trait {
 	/// The allowed extrinsic position for `note_offline` inherent.
 	const NOTE_OFFLINE_POSITION: u32;
 
+	/// Type for all log entries of this module.
+	type Log: From<Log<Self>> + Into<system::DigestItemOf<Self>>;
+
 	type SessionKey: Parameter + Default + MaybeSerializeDebug;
 	type OnOfflineValidator: OnOfflineValidator;
 }
 
+decl_storage! {
+	trait Store for Module<T: Trait> as Consensus {
+		// Authorities set actual at the block execution start. IsSome only if
+		// the set has been changed.
+		OriginalAuthorities: Vec<T::SessionKey>;
+	}
+}
+
 decl_module! {
 	pub struct Module<T: Trait>;
 
@@ -149,12 +210,40 @@ impl<T: Trait> Module<T> {
 	///
 	/// Called by `next_session` only.
 	pub fn set_authorities(authorities: &[T::SessionKey]) {
-		AuthorityStorageVec::<T::SessionKey>::set_items(authorities);
+		let current_authorities = AuthorityStorageVec::<T::SessionKey>::items();
+		if current_authorities != authorities {
+			Self::save_original_authorities(Some(current_authorities));
+			AuthorityStorageVec::<T::SessionKey>::set_items(authorities);
+		}
 	}
 
 	/// Set a single authority by index.
 	pub fn set_authority(index: u32, key: &T::SessionKey) {
-		AuthorityStorageVec::<T::SessionKey>::set_item(index, key);
+		let current_authority = AuthorityStorageVec::<T::SessionKey>::item(index);
+		if current_authority != *key {
+			Self::save_original_authorities(None);
+			AuthorityStorageVec::<T::SessionKey>::set_item(index, key);
+		}
+	}
+
+	/// Save original authorities set.
+	fn save_original_authorities(current_authorities: Option<Vec<T::SessionKey>>) {
+		if OriginalAuthorities::<T>::get().is_some() {
+			// if we have already saved original set before, do not overwrite
+			return;
+		}
+
+		<OriginalAuthorities<T>>::put(current_authorities.unwrap_or_else(||
+			AuthorityStorageVec::<T::SessionKey>::items()));
+	}
+}
+
+/// Finalization hook for the consensus module.
+impl<T: Trait> OnFinalise<T::BlockNumber> for Module<T> {
+	fn on_finalise(_n: T::BlockNumber) {
+		if let Some(_) = <OriginalAuthorities<T>>::take() {
+			// TODO: call Self::deposit_log
+		}
 	}
 }
 
diff --git a/substrate/runtime/executive/src/lib.rs b/substrate/runtime/executive/src/lib.rs
index caaf91a75617d..9e0db49391fa2 100644
--- a/substrate/runtime/executive/src/lib.rs
+++ b/substrate/runtime/executive/src/lib.rs
@@ -255,6 +255,7 @@ mod tests {
 	pub struct Test;
 	impl consensus::Trait for Test {
 		const NOTE_OFFLINE_POSITION: u32 = 1;
+		type Log = u64;
 		type SessionKey = u64;
 		type OnOfflineValidator = staking::Module<Test>;
 	}
diff --git a/substrate/runtime/primitives/src/generic.rs b/substrate/runtime/primitives/src/generic.rs
index efcc52fbecb49..6305bac8d6c99 100644
--- a/substrate/runtime/primitives/src/generic.rs
+++ b/substrate/runtime/primitives/src/generic.rs
@@ -26,7 +26,7 @@ use rstd::prelude::*;
 use codec::{Decode, Encode, Codec, Input, Output};
 use runtime_support::AuxDispatchable;
 use traits::{self, Member, SimpleArithmetic, SimpleBitOps, MaybeDisplay, Block as BlockT,
-	Header as HeaderT, Hash as HashT};
+	Header as HeaderT, Hash as HashT, DigestItem as DigestItemT};
 use rstd::ops;
 use bft::Justification;
 
@@ -208,16 +208,27 @@ where
 	}
 }
 
-#[derive(Default, PartialEq, Eq, Clone, Encode, Decode)]
+#[derive(PartialEq, Eq, Clone, Encode, Decode)]
 #[cfg_attr(feature = "std", derive(Debug, Serialize, Deserialize))]
 pub struct Digest<Item> {
 	pub logs: Vec<Item>,
 }
 
+impl<Item> Default for Digest<Item> {
+	fn default() -> Self {
+		Digest { logs: Vec::new(), }
+	}
+}
+
 impl<Item> traits::Digest for Digest<Item> where
-	Item: Member + Default + Codec
+	Item: DigestItemT + Codec
 {
 	type Item = Item;
+
+	fn logs(&self) -> &[Self::Item] {
+		&self.logs
+	}
+
 	fn push(&mut self, item: Self::Item) {
 		self.logs.push(item);
 	}
@@ -317,7 +328,7 @@ impl<Number, Hash, DigestItem> Encode for Header<Number, Hash, DigestItem> where
 impl<Number, Hash, DigestItem> traits::Header for Header<Number, Hash, DigestItem> where
 	Number: Member + ::rstd::hash::Hash + Copy + Codec + MaybeDisplay + SimpleArithmetic + Codec,
 	Hash: HashT,
-	DigestItem: Member + Default + Codec,
+	DigestItem: DigestItemT + Codec,
 	Hash::Output: Default + ::rstd::hash::Hash + Copy + Member + MaybeDisplay + SimpleBitOps + Codec,
  {
 	type Number = Number;
@@ -356,7 +367,7 @@ impl<Number, Hash, DigestItem> traits::Header for Header<Number, Hash, DigestIte
 impl<Number, Hash, DigestItem> Header<Number, Hash, DigestItem> where
 	Number: Member + ::rstd::hash::Hash + Copy + Codec + MaybeDisplay + SimpleArithmetic + Codec,
 	Hash: HashT,
-	DigestItem: Member + Default + Codec,
+	DigestItem: DigestItemT + Codec,
 	Hash::Output: Default + ::rstd::hash::Hash + Copy + Member + MaybeDisplay + SimpleBitOps + Codec,
  {
 	/// Convenience helper for computing the hash of the header without having
diff --git a/substrate/runtime/primitives/src/testing.rs b/substrate/runtime/primitives/src/testing.rs
index b1dcef2eadbef..9ac86d7747c82 100644
--- a/substrate/runtime/primitives/src/testing.rs
+++ b/substrate/runtime/primitives/src/testing.rs
@@ -31,11 +31,20 @@ pub struct Digest {
 
 impl traits::Digest for Digest {
 	type Item = u64;
+
+	fn logs(&self) -> &[Self::Item] {
+		&self.logs
+	}
+
 	fn push(&mut self, item: Self::Item) {
 		self.logs.push(item);
 	}
 }
 
+impl traits::DigestItem for u64 {
+	type AuthoritiesChange = ();
+}
+
 #[derive(PartialEq, Eq, Clone, Serialize, Deserialize, Debug, Encode, Decode)]
 #[serde(rename_all = "camelCase")]
 #[serde(deny_unknown_fields)]
diff --git a/substrate/runtime/primitives/src/traits.rs b/substrate/runtime/primitives/src/traits.rs
index 848d7bcc35293..fbfdfa8a8d74a 100644
--- a/substrate/runtime/primitives/src/traits.rs
+++ b/substrate/runtime/primitives/src/traits.rs
@@ -317,13 +317,6 @@ impl<T> MaybeDisplay for T {}
 pub trait Member: Send + Sync + Sized + MaybeSerializeDebug + Eq + PartialEq + Clone + 'static {}
 impl<T: Send + Sync + Sized + MaybeSerializeDebug + Eq + PartialEq + Clone + 'static> Member for T {}
 
-/// Something that acts like a `Digest` - it can have `Log`s `push`ed onto it and these `Log`s are
-/// each `Codec`.
-pub trait Digest {
-	type Item: Member;
-	fn push(&mut self, item: Self::Item);
-}
-
 /// Something which fulfills the abstract idea of a Substrate header. It has types for a `Number`,
 /// a `Hash` and a `Digest`. It provides access to an `extrinsics_root`, `state_root` and
 /// `parent_hash`, as well as a `digest` and a block `number`.
@@ -333,7 +326,7 @@ pub trait Header: Clone + Send + Sync + Codec + Eq + MaybeSerializeDebug + 'stat
 	type Number: Member + ::rstd::hash::Hash + Copy + MaybeDisplay + SimpleArithmetic + Codec;
 	type Hash: Member + ::rstd::hash::Hash + Copy + MaybeDisplay + Default + SimpleBitOps + Codec + AsRef<[u8]>;
 	type Hashing: Hash<Output = Self::Hash>;
-	type Digest: Member + Default;
+	type Digest: Digest;
 
 	fn new(
 		number: Self::Number,
@@ -429,3 +422,49 @@ pub trait Applyable: Sized + Send + Sync {
 	fn sender(&self) -> &Self::AccountId;
 	fn apply(self) -> Result<(), &'static str>;
 }
+
+/// Something that acts like a `Digest` - it can have `Log`s `push`ed onto it and these `Log`s are
+/// each `Codec`.
+pub trait Digest: Member + Default {
+	type Item: DigestItem;
+	fn logs(&self) -> &[Self::Item];
+	fn push(&mut self, item: Self::Item);
+}
+
+/// Single digest item. Could be any type that implements `Member` and provides methods
+/// for casting member to 'system' log items, known to substrate.
+///
+/// If the runtime does not supports some 'system' items, use `()` as a stub.
+pub trait DigestItem: Member {
+	/// Events of this type is raised by the runtime when set of authorities is changed.
+	/// Provides access to the new set of authorities.
+	type AuthoritiesChange: AuthoritiesChangeDigest; // TODO: = () when associated type defaults are stabilized
+
+ 	/// Returns Some if the entry is the `AuthoritiesChange` entry.
+	fn as_authorities_change(&self) -> Option<&Self::AuthoritiesChange> {
+		None
+	}
+}
+
+/// Authorities change digest item. Created when the set of authorities is changed
+/// within the runtime.
+pub trait AuthoritiesChangeDigest {
+	/// Type of authority Id.
+	type AuthorityId: Member;
+
+	/// Get reference to the new authorities set.
+	fn authorities(&self) -> &[Self::AuthorityId];
+}
+
+/// Stub implementations for the digest item that is never created and used.
+///
+/// Should be used as a stub for items that are not supported by runtimes.
+impl DigestItem for () {
+	type AuthoritiesChange = ();
+}
+
+impl AuthoritiesChangeDigest for () {
+	type AuthorityId = ();
+
+	fn authorities(&self) -> &[Self::AuthorityId] { unreachable!("() is never created") }
+}
diff --git a/substrate/runtime/session/src/lib.rs b/substrate/runtime/session/src/lib.rs
index 1e4ac22e78197..fc5bb0438f564 100644
--- a/substrate/runtime/session/src/lib.rs
+++ b/substrate/runtime/session/src/lib.rs
@@ -295,6 +295,7 @@ mod tests {
 	pub struct Test;
 	impl consensus::Trait for Test {
 		const NOTE_OFFLINE_POSITION: u32 = 1;
+		type Log = u64;
 		type SessionKey = u64;
 		type OnOfflineValidator = ();
 	}
diff --git a/substrate/runtime/staking/src/mock.rs b/substrate/runtime/staking/src/mock.rs
index 1f8cc8e02129f..b8ae013b38dfc 100644
--- a/substrate/runtime/staking/src/mock.rs
+++ b/substrate/runtime/staking/src/mock.rs
@@ -30,6 +30,7 @@ use {GenesisConfig, Module, Trait, consensus, session, system, timestamp, balanc
 pub struct Test;
 impl consensus::Trait for Test {
 	const NOTE_OFFLINE_POSITION: u32 = 1;
+	type Log = u64;
 	type SessionKey = u64;
 	type OnOfflineValidator = ();
 }
diff --git a/substrate/runtime/system/src/lib.rs b/substrate/runtime/system/src/lib.rs
index 02c937b190fe0..617852b35d313 100644
--- a/substrate/runtime/system/src/lib.rs
+++ b/substrate/runtime/system/src/lib.rs
@@ -86,6 +86,8 @@ pub trait Trait: Eq + Clone {
 	type Event: Parameter + Member + From<Event>;
 }
 
+pub type DigestItemOf<T> = <<T as Trait>::Digest as traits::Digest>::Item;
+
 decl_module! {
 	pub struct Module<T: Trait>;
 }
diff --git a/substrate/runtime/timestamp/src/lib.rs b/substrate/runtime/timestamp/src/lib.rs
index 5d9fdad118eb5..e7ea230a76f4c 100644
--- a/substrate/runtime/timestamp/src/lib.rs
+++ b/substrate/runtime/timestamp/src/lib.rs
@@ -161,6 +161,7 @@ mod tests {
 	}
 	impl consensus::Trait for Test {
 		const NOTE_OFFLINE_POSITION: u32 = 1;
+		type Log = u64;
 		type SessionKey = u64;
 		type OnOfflineValidator = ();
 	}
diff --git a/substrate/test-runtime/src/lib.rs b/substrate/test-runtime/src/lib.rs
index 9f0d1be93da83..0bf753a9443a4 100644
--- a/substrate/test-runtime/src/lib.rs
+++ b/substrate/test-runtime/src/lib.rs
@@ -112,11 +112,11 @@ pub type BlockNumber = u64;
 /// Index of a transaction.
 pub type Index = u64;
 /// The digest of a block.
-pub type Digest = runtime_primitives::generic::Digest<Vec<u8>>;
+pub type Digest = runtime_primitives::generic::Digest<()>;
 /// A test block.
 pub type Block = runtime_primitives::generic::Block<Header, Extrinsic>;
 /// A test block's header.
-pub type Header = runtime_primitives::generic::Header<BlockNumber, BlakeTwo256, Vec<u8>>;
+pub type Header = runtime_primitives::generic::Header<BlockNumber, BlakeTwo256, ()>;
 
 /// Run whatever tests we have.
 pub fn run_tests(mut input: &[u8]) -> Vec<u8> {
diff --git a/substrate/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.compact.wasm b/substrate/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.compact.wasm
index 77804d43d0eb7..0afb7c9f18416 100644
Binary files a/substrate/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.compact.wasm and b/substrate/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.compact.wasm differ
diff --git a/substrate/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.wasm b/substrate/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.wasm
index ca4435aba5534..674df04b2bdbf 100755
Binary files a/substrate/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.wasm and b/substrate/test-runtime/wasm/target/wasm32-unknown-unknown/release/substrate_test_runtime.wasm differ