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 2823d62ae5865..3a11483da2abd 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 d95558e2ed6ac..4a4d907df7d04 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/polkadot/api/src/lib.rs b/polkadot/api/src/lib.rs
index bf747624c3945..731c19a49637d 100644
--- a/polkadot/api/src/lib.rs
+++ b/polkadot/api/src/lib.rs
@@ -153,17 +153,30 @@ impl CheckedBlockId for CheckedId {
 	}
 }
 
-// set up the necessary scaffolding to execute the runtime.
+// set up the necessary scaffolding to execute a set of calls to the runtime.
+// this creates a new block on top of the given ID and initialises it.
 macro_rules! with_runtime {
 	($client: ident, $at: expr, $exec: expr) => {{
-		$client.state_at($at.block_id()).map_err(Error::from).and_then(|state| {
+		let parent = $at.block_id();
+		let header = Header {
+			parent_hash: $client.block_hash_from_id(parent)?.ok_or(ErrorKind::UnknownBlock(*parent))?,
+			number: $client.block_number_from_id(parent)?.ok_or(ErrorKind::UnknownBlock(*parent))? + 1,
+			state_root: Default::default(),
+			extrinsics_root: Default::default(),
+			digest: Default::default(),
+		};
+
+		$client.state_at(parent).map_err(Error::from).and_then(|state| {
 			let mut changes = Default::default();
 			let mut ext = state_machine::Ext {
 				overlay: &mut changes,
 				backend: &state,
 			};
 
-			::substrate_executor::with_native_environment(&mut ext, $exec).map_err(Into::into)
+			::substrate_executor::with_native_environment(&mut ext, || {
+				::runtime::Executive::initialise_block(&header);
+				($exec)()
+			}).map_err(Into::into)
 		})
 	}}
 }
@@ -196,16 +209,7 @@ impl<B: Backend> PolkadotApi for Client<B, NativeExecutor<LocalDispatch>>
 	}
 
 	fn duty_roster(&self, at: &CheckedId) -> Result<DutyRoster> {
-		// duty roster can only be queried at the start of a block,
-		// so we create a dummy.
-		let id = at.block_id();
-		let parent_hash = self.block_hash_from_id(id)?.ok_or(ErrorKind::UnknownBlock(*id))?;
-		let number = self.block_number_from_id(id)?.ok_or(ErrorKind::UnknownBlock(*id))? + 1;
-
-		with_runtime!(self, at, || {
-			::runtime::System::initialise(&number, &parent_hash, &Default::default());
-			::runtime::Parachains::calculate_duty_roster()
-		})
+		with_runtime!(self, at, ::runtime::Parachains::calculate_duty_roster)
 	}
 
 	fn timestamp(&self, at: &CheckedId) -> Result<Timestamp> {
@@ -422,4 +426,12 @@ mod tests {
 	fn fails_to_check_id_for_unknown_block() {
 		assert!(client().check_id(BlockId::Number(100)).is_err());
 	}
+
+	#[test]
+	fn gets_random_seed_with_genesis() {
+		let client = client();
+
+		let id = client.check_id(BlockId::Number(0)).unwrap();
+		assert!(client.random_seed(&id).is_ok());
+	}
 }
diff --git a/polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.compact.wasm b/polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.compact.wasm
index 05ff2f4505ecc..3f05418e5e6e6 100644
Binary files a/polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.compact.wasm and b/polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.compact.wasm differ
diff --git a/polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.wasm b/polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.wasm
index 4bb8fff698606..4d67e2c5514a7 100755
Binary files a/polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_runtime.wasm and b/polkadot/runtime/wasm/target/wasm32-unknown-unknown/release/polkadot_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 c7e6b0e25f79e..7c16bd90033dd 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 d9d13ededb235..6c6b8d63a9e28 100755
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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 59a333c876829..c53bc9dd885f9 100644
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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 c80254075723f..063e3c5ed25c9 100755
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