diff --git a/primitives/src/parachain.rs b/primitives/src/parachain.rs
index 606d5668e9b8..dabd2fc6b18f 100644
--- a/primitives/src/parachain.rs
+++ b/primitives/src/parachain.rs
@@ -421,7 +421,7 @@ substrate_client::decl_runtime_apis! {
 		/// Get the current duty roster.
 		fn duty_roster() -> DutyRoster;
 		/// Get the currently active parachains.
-		fn active_parachains() -> Vec<Id>;
+		fn active_parachains() -> Vec<(Id, Option<CollatorId>)>;
 		/// Get the given parachain's status.
 		fn parachain_status(id: Id) -> Option<Status>;
 		/// Get the given parachain's head code blob.
diff --git a/runtime/src/lib.rs b/runtime/src/lib.rs
index 6671e804964c..c071ce7f9b0d 100644
--- a/runtime/src/lib.rs
+++ b/runtime/src/lib.rs
@@ -47,6 +47,7 @@ use grandpa::{
 	AuthorityId as GrandpaId, fg_primitives::{self, ScheduledChange}
 };
 use elections::VoteIndex;
+use session::PeriodicSessions;
 #[cfg(any(feature = "std", test))]
 use version::NativeVersion;
 use substrate_primitives::OpaqueMetadata;
@@ -106,6 +107,7 @@ parameter_types! {
 
 impl system::Trait for Runtime {
 	type Origin = Origin;
+	type Call = Call;
 	type Index = Nonce;
 	type BlockNumber = BlockNumber;
 	type Hash = Hash;
@@ -165,9 +167,13 @@ impl balances::Trait for Runtime {
 	type WeightToFee = WeightToFee;
 }
 
+parameter_types! {
+	pub const MinimumPeriod: Moment = SLOT_DURATION / 2;
+}
 impl timestamp::Trait for Runtime {
 	type Moment = Moment;
 	type OnTimestampSet = Aura;
+	type MinimumPeriod = MinimumPeriod;
 }
 
 parameter_types! {
@@ -207,10 +213,14 @@ impl_opaque_keys! {
 impl session::Trait for Runtime {
 	type OnSessionEnding = Staking;
 	type SessionHandler = SessionHandlers;
-	type ShouldEndSession = session::PeriodicSessions<Period, Offset>;
+	type ShouldEndSession = PeriodicSessions<Period, Offset>;
 	type Event = Event;
 	type Keys = SessionKeys;
+	type ValidatorId = AccountId;
+	type ValidatorIdOf = staking::StashOf<Self>;
+	type SelectInitialValidators = Staking;
 }
+
 impl session::historical::Trait for Runtime {
 	type FullIdentification = staking::Exposure<AccountId, Balance>;
 	type FullIdentificationOf = staking::ExposureOf<Runtime>;
@@ -344,6 +354,8 @@ impl parachains::Trait for Runtime {
 	type Origin = Origin;
 	type Call = Call;
 	type ParachainCurrency = Balances;
+	type ActiveParachains = Registrar;
+	type Registrar = Registrar;
 }
 
 parameter_types! {
@@ -493,8 +505,8 @@ impl_runtime_apis! {
 		fn duty_roster() -> parachain::DutyRoster {
 			Parachains::calculate_duty_roster()
 		}
-		fn active_parachains() -> Vec<parachain::Id> {
-			Parachains::active_parachains()
+		fn active_parachains() -> Vec<(parachain::Id, Option<parachain::CollatorId>)> {
+			Registrar::active_parachains()
 		}
 		fn parachain_status(id: parachain::Id) -> Option<parachain::Status> {
 			Parachains::parachain_status(&id)
diff --git a/runtime/src/parachains.rs b/runtime/src/parachains.rs
index 963adcc0f9cd..678d6d48650e 100644
--- a/runtime/src/parachains.rs
+++ b/runtime/src/parachains.rs
@@ -198,7 +198,7 @@ decl_module! {
 						);
 
 						// must be unknown since active parachains are always sorted.
-						let (_, maybe_required_collator, origins) = iter.find(|para| para.0 == id)
+						let (_, maybe_required_collator) = iter.find(|para| para.0 == id)
 							.ok_or("candidate for unregistered parachain {}")?;
 
 						if let Some(required_collator) = maybe_required_collator {
@@ -207,7 +207,6 @@ decl_module! {
 
 						Self::check_upward_messages(
 							id,
-							origins,
 							&head.candidate.upward_messages,
 							MAX_QUEUE_COUNT,
 							WATERMARK_QUEUE_SIZE,
diff --git a/runtime/src/registrar.rs b/runtime/src/registrar.rs
index e231a545fd88..f5efae7a7880 100644
--- a/runtime/src/registrar.rs
+++ b/runtime/src/registrar.rs
@@ -336,11 +336,14 @@ impl<T: Trait + Send + Sync> SignedExtension for LimitParathreadCommits<T> where
 	type AccountId = T::AccountId;
 	type Call = <T as system::Trait>::Call;
 	type AdditionalSigned = ();
+	fn additional_signed(&self) -> rstd::result::Result<Self::AdditionalSigned, &'static str> {
+		Ok(())
+	}
 
 	fn validate(
 		&self,
-		call: &Self::Call,
 		who: &Self::AccountId,
+		call: &Self::Call,
 		info: DispatchInfo,
 		len: usize,
 	) -> rstd::result::Result<ValidTransaction, DispatchError> {
diff --git a/runtime/src/slots.rs b/runtime/src/slots.rs
index 7e98a9da8c0c..a56c29a4fc39 100644
--- a/runtime/src/slots.rs
+++ b/runtime/src/slots.rs
@@ -27,7 +27,7 @@ use srml_support::{
 	traits::{Currency, ReservableCurrency, WithdrawReason, ExistenceRequirement, Get}
 };
 use primitives::parachain::{
-	AccountIdConversion, OnSwap, PARACHAIN_INFO, Id as ParaId, ActiveParas
+	AccountIdConversion, OnSwap, PARACHAIN_INFO, Id as ParaId
 };
 use crate::registrar::Registrar;
 use system::{ensure_signed, ensure_root};