diff --git a/eth2/attester/src/lib.rs b/eth2/attester/src/lib.rs
index 5bffd0c503..8838f022d9 100644
--- a/eth2/attester/src/lib.rs
+++ b/eth2/attester/src/lib.rs
@@ -2,8 +2,9 @@ pub mod test_utils;
 mod traits;
 
 use slot_clock::SlotClock;
+use ssz::TreeHash;
 use std::sync::Arc;
-use types::{AttestationData, FreeAttestation, Signature, Slot};
+use types::{AttestationData, AttestationDataAndCustodyBit, FreeAttestation, Signature, Slot};
 
 pub use self::traits::{
     BeaconNode, BeaconNodeError, DutiesReader, DutiesReaderError, PublishOutcome, Signer,
@@ -137,10 +138,14 @@ impl<T: SlotClock, U: BeaconNode, V: DutiesReader, W: Signer> Attester<T, U, V,
     fn sign_attestation_data(&mut self, attestation_data: &AttestationData) -> Option<Signature> {
         self.store_produce(attestation_data);
 
-        self.signer.sign_attestation_message(
-            &attestation_data.signable_message(PHASE_0_CUSTODY_BIT)[..],
-            DOMAIN_ATTESTATION,
-        )
+        let message = AttestationDataAndCustodyBit {
+            data: attestation_data.clone(),
+            custody_bit: PHASE_0_CUSTODY_BIT,
+        }
+        .hash_tree_root();
+
+        self.signer
+            .sign_attestation_message(&message[..], DOMAIN_ATTESTATION)
     }
 
     /// Returns `true` if signing some attestation_data is safe (non-slashable).
diff --git a/eth2/block_proposer/src/lib.rs b/eth2/block_proposer/src/lib.rs
index cea8556272..55461d986a 100644
--- a/eth2/block_proposer/src/lib.rs
+++ b/eth2/block_proposer/src/lib.rs
@@ -3,13 +3,17 @@ mod traits;
 
 use int_to_bytes::int_to_bytes32;
 use slot_clock::SlotClock;
+use ssz::SignedRoot;
 use std::sync::Arc;
-use types::{BeaconBlock, ChainSpec, Slot};
+use types::{BeaconBlock, ChainSpec, Hash256, Proposal, Slot};
 
 pub use self::traits::{
     BeaconNode, BeaconNodeError, DutiesReader, DutiesReaderError, PublishOutcome, Signer,
 };
 
+//TODO: obtain the correct domain using a `Fork`.
+pub const TEMPORARY_DOMAIN_VALUE: u64 = 0;
+
 #[derive(Debug, PartialEq)]
 pub enum PollOutcome {
     /// A new block was produced.
@@ -136,7 +140,7 @@ impl<T: SlotClock, U: BeaconNode, V: DutiesReader, W: Signer> BlockProducer<T, U
 
             match self
                 .signer
-                .sign_randao_reveal(&message, self.spec.domain_randao)
+                .sign_randao_reveal(&message, TEMPORARY_DOMAIN_VALUE)
             {
                 None => return Ok(PollOutcome::SignerRejection(slot)),
                 Some(signature) => signature,
@@ -169,10 +173,17 @@ impl<T: SlotClock, U: BeaconNode, V: DutiesReader, W: Signer> BlockProducer<T, U
     fn sign_block(&mut self, mut block: BeaconBlock) -> Option<BeaconBlock> {
         self.store_produce(&block);
 
-        match self.signer.sign_block_proposal(
-            &block.proposal_root(&self.spec)[..],
-            self.spec.domain_proposal,
-        ) {
+        let proposal = Proposal {
+            slot: block.slot,
+            shard: self.spec.beacon_chain_shard_number,
+            block_root: Hash256::from_slice(&block.signed_root()[..]),
+            signature: block.signature.clone(),
+        };
+
+        match self
+            .signer
+            .sign_block_proposal(&proposal.signed_root()[..], TEMPORARY_DOMAIN_VALUE)
+        {
             None => None,
             Some(signature) => {
                 block.signature = signature;