diff --git a/beacon_node/beacon_chain/test_harness/src/validator_harness/direct_duties.rs b/beacon_node/beacon_chain/test_harness/src/validator_harness/direct_duties.rs
index 5bed59531..dec93c334 100644
--- a/beacon_node/beacon_chain/test_harness/src/validator_harness/direct_duties.rs
+++ b/beacon_node/beacon_chain/test_harness/src/validator_harness/direct_duties.rs
@@ -9,7 +9,7 @@ use db::ClientDB;
 use fork_choice::ForkChoice;
 use slot_clock::SlotClock;
 use std::sync::Arc;
-use types::{PublicKey, Slot};
+use types::{Fork, PublicKey, Slot};
 
 /// Connects directly to a borrowed `BeaconChain` and reads attester/proposer duties directly from
 /// it.
@@ -40,6 +40,10 @@ impl<T: ClientDB, U: SlotClock, F: ForkChoice> ProducerDutiesReader for DirectDu
             Err(_) => Err(ProducerDutiesReaderError::UnknownEpoch),
         }
     }
+
+    fn fork(&self) -> Result<Fork, ProducerDutiesReaderError> {
+        Ok(self.beacon_chain.state.read().fork.clone())
+    }
 }
 
 impl<T: ClientDB, U: SlotClock, F: ForkChoice> AttesterDutiesReader for DirectDuties<T, U, F> {
diff --git a/eth2/block_proposer/src/lib.rs b/eth2/block_proposer/src/lib.rs
index 55461d986..5cddbaedc 100644
--- a/eth2/block_proposer/src/lib.rs
+++ b/eth2/block_proposer/src/lib.rs
@@ -1,19 +1,15 @@
 pub mod test_utils;
 mod traits;
 
-use int_to_bytes::int_to_bytes32;
 use slot_clock::SlotClock;
-use ssz::SignedRoot;
+use ssz::{SignedRoot, TreeHash};
 use std::sync::Arc;
-use types::{BeaconBlock, ChainSpec, Hash256, Proposal, Slot};
+use types::{BeaconBlock, ChainSpec, Domain, 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.
@@ -32,6 +28,8 @@ pub enum PollOutcome {
     SignerRejection(Slot),
     /// The public key for this validator is not an active validator.
     ValidatorIsUnknown(Slot),
+    /// Unable to determine a `Fork` for signature domain generation.
+    UnableToGetFork(Slot),
 }
 
 #[derive(Debug, PartialEq)]
@@ -134,14 +132,20 @@ impl<T: SlotClock, U: BeaconNode, V: DutiesReader, W: Signer> BlockProducer<T, U
     /// The slash-protection code is not yet implemented. There is zero protection against
     /// slashing.
     fn produce_block(&mut self, slot: Slot) -> Result<PollOutcome, Error> {
+        let fork = match self.epoch_map.fork() {
+            Ok(fork) => fork,
+            Err(_) => return Ok(PollOutcome::UnableToGetFork(slot)),
+        };
+
         let randao_reveal = {
             // TODO: add domain, etc to this message. Also ensure result matches `into_to_bytes32`.
-            let message = int_to_bytes32(slot.epoch(self.spec.slots_per_epoch).as_u64());
+            let message = slot.epoch(self.spec.slots_per_epoch).hash_tree_root();
 
-            match self
-                .signer
-                .sign_randao_reveal(&message, TEMPORARY_DOMAIN_VALUE)
-            {
+            match self.signer.sign_randao_reveal(
+                &message,
+                self.spec
+                    .get_domain(slot.epoch(self.spec.slots_per_epoch), Domain::Randao, &fork),
+            ) {
                 None => return Ok(PollOutcome::SignerRejection(slot)),
                 Some(signature) => signature,
             }
@@ -152,7 +156,12 @@ impl<T: SlotClock, U: BeaconNode, V: DutiesReader, W: Signer> BlockProducer<T, U
             .produce_beacon_block(slot, &randao_reveal)?
         {
             if self.safe_to_produce(&block) {
-                if let Some(block) = self.sign_block(block) {
+                let domain = self.spec.get_domain(
+                    slot.epoch(self.spec.slots_per_epoch),
+                    Domain::Proposal,
+                    &fork,
+                );
+                if let Some(block) = self.sign_block(block, domain) {
                     self.beacon_node.publish_beacon_block(block)?;
                     Ok(PollOutcome::BlockProduced(slot))
                 } else {
@@ -170,7 +179,7 @@ impl<T: SlotClock, U: BeaconNode, V: DutiesReader, W: Signer> BlockProducer<T, U
     ///
     /// Important: this function will not check to ensure the block is not slashable. This must be
     /// done upstream.
-    fn sign_block(&mut self, mut block: BeaconBlock) -> Option<BeaconBlock> {
+    fn sign_block(&mut self, mut block: BeaconBlock, domain: u64) -> Option<BeaconBlock> {
         self.store_produce(&block);
 
         let proposal = Proposal {
@@ -182,7 +191,7 @@ impl<T: SlotClock, U: BeaconNode, V: DutiesReader, W: Signer> BlockProducer<T, U
 
         match self
             .signer
-            .sign_block_proposal(&proposal.signed_root()[..], TEMPORARY_DOMAIN_VALUE)
+            .sign_block_proposal(&proposal.signed_root()[..], domain)
         {
             None => None,
             Some(signature) => {
diff --git a/eth2/block_proposer/src/test_utils/epoch_map.rs b/eth2/block_proposer/src/test_utils/epoch_map.rs
index f7d8dcdcb..6658c7526 100644
--- a/eth2/block_proposer/src/test_utils/epoch_map.rs
+++ b/eth2/block_proposer/src/test_utils/epoch_map.rs
@@ -1,6 +1,6 @@
 use crate::{DutiesReader, DutiesReaderError};
 use std::collections::HashMap;
-use types::{Epoch, Slot};
+use types::{Epoch, Fork, Slot};
 
 pub struct EpochMap {
     slots_per_epoch: u64,
@@ -25,4 +25,12 @@ impl DutiesReader for EpochMap {
             _ => Err(DutiesReaderError::UnknownEpoch),
         }
     }
+
+    fn fork(&self) -> Result<Fork, DutiesReaderError> {
+        Ok(Fork {
+            previous_version: 0,
+            current_version: 0,
+            epoch: Epoch::new(0),
+        })
+    }
 }
diff --git a/eth2/block_proposer/src/traits.rs b/eth2/block_proposer/src/traits.rs
index c6e57d833..1c0da9acf 100644
--- a/eth2/block_proposer/src/traits.rs
+++ b/eth2/block_proposer/src/traits.rs
@@ -1,4 +1,4 @@
-use types::{BeaconBlock, Signature, Slot};
+use types::{BeaconBlock, Fork, Signature, Slot};
 
 #[derive(Debug, PartialEq, Clone)]
 pub enum BeaconNodeError {
@@ -40,6 +40,7 @@ pub enum DutiesReaderError {
 /// Informs a validator of their duties (e.g., block production).
 pub trait DutiesReader: Send + Sync {
     fn is_block_production_slot(&self, slot: Slot) -> Result<bool, DutiesReaderError>;
+    fn fork(&self) -> Result<Fork, DutiesReaderError>;
 }
 
 /// Signs message using an internally-maintained private key.
diff --git a/validator_client/src/block_producer_service/mod.rs b/validator_client/src/block_producer_service/mod.rs
index bd1e691cb..91e7606a7 100644
--- a/validator_client/src/block_producer_service/mod.rs
+++ b/validator_client/src/block_producer_service/mod.rs
@@ -50,6 +50,9 @@ impl<T: SlotClock, U: BeaconNode, V: DutiesReader, W: Signer> BlockProducerServi
                 Ok(BlockProducerPollOutcome::ValidatorIsUnknown(slot)) => {
                     error!(self.log, "The Beacon Node does not recognise the validator"; "slot" => slot)
                 }
+                Ok(BlockProducerPollOutcome::UnableToGetFork(slot)) => {
+                    error!(self.log, "Unable to get a `Fork` struct to generate signature domains"; "slot" => slot)
+                }
             };
 
             std::thread::sleep(Duration::from_millis(self.poll_interval_millis));
diff --git a/validator_client/src/duties/epoch_duties.rs b/validator_client/src/duties/epoch_duties.rs
index d1bbfa156..35668b4a9 100644
--- a/validator_client/src/duties/epoch_duties.rs
+++ b/validator_client/src/duties/epoch_duties.rs
@@ -1,7 +1,7 @@
 use block_proposer::{DutiesReader, DutiesReaderError};
 use std::collections::HashMap;
 use std::sync::RwLock;
-use types::{Epoch, Slot};
+use types::{Epoch, Fork, Slot};
 
 /// The information required for a validator to propose and attest during some epoch.
 ///
@@ -75,6 +75,17 @@ impl DutiesReader for EpochDutiesMap {
             .ok_or_else(|| DutiesReaderError::UnknownEpoch)?;
         Ok(duties.is_block_production_slot(slot))
     }
+
+    fn fork(&self) -> Result<Fork, DutiesReaderError> {
+        // TODO: this is garbage data.
+        //
+        // It will almost certainly cause signatures to fail verification.
+        Ok(Fork {
+            previous_version: 0,
+            current_version: 0,
+            epoch: Epoch::new(0),
+        })
+    }
 }
 
 // TODO: add tests.