diff --git a/validator_client/src/block_producer/grpc.rs b/validator_client/src/block_producer/grpc.rs
index ca47ee3a6b..20ced3d0c3 100644
--- a/validator_client/src/block_producer/grpc.rs
+++ b/validator_client/src/block_producer/grpc.rs
@@ -63,7 +63,7 @@ impl BeaconNode for BeaconBlockServiceClient {
         let mut grpc_block = GrpcBeaconBlock::new();
         grpc_block.set_slot(block.slot);
         grpc_block.set_block_root(vec![0]);
-        grpc_block.set_randao_reveal(block.randao_reveal.to_vec());
+        grpc_block.set_randao_reveal(ssz_encode(&block.randao_reveal));
         grpc_block.set_signature(ssz_encode(&block.signature));
 
         req.set_block(grpc_block);
diff --git a/validator_client/src/block_producer/mod.rs b/validator_client/src/block_producer/mod.rs
index f3cd0199bb..e0ea220b6a 100644
--- a/validator_client/src/block_producer/mod.rs
+++ b/validator_client/src/block_producer/mod.rs
@@ -2,10 +2,9 @@ mod grpc;
 mod service;
 #[cfg(test)]
 mod test_node;
-mod traits;
+pub mod traits;
 
-use self::traits::{BeaconNode, BeaconNodeError};
-use super::EpochDutiesMap;
+use self::traits::{BeaconNode, BeaconNodeError, DutiesReader, DutiesReaderError};
 use slot_clock::SlotClock;
 use spec::ChainSpec;
 use std::sync::{Arc, RwLock};
@@ -45,19 +44,19 @@ pub enum Error {
 /// Ensures that messages are not slashable.
 ///
 /// Relies upon an external service to keep the `EpochDutiesMap` updated.
-pub struct BlockProducer<T: SlotClock, U: BeaconNode> {
+pub struct BlockProducer<T: SlotClock, U: BeaconNode, V: DutiesReader> {
     pub last_processed_slot: u64,
     spec: Arc<ChainSpec>,
-    epoch_map: Arc<RwLock<EpochDutiesMap>>,
+    epoch_map: Arc<V>,
     slot_clock: Arc<RwLock<T>>,
     beacon_node: Arc<U>,
 }
 
-impl<T: SlotClock, U: BeaconNode> BlockProducer<T, U> {
+impl<T: SlotClock, U: BeaconNode, V: DutiesReader> BlockProducer<T, U, V> {
     /// Returns a new instance where `last_processed_slot == 0`.
     pub fn new(
         spec: Arc<ChainSpec>,
-        epoch_map: Arc<RwLock<EpochDutiesMap>>,
+        epoch_map: Arc<V>,
         slot_clock: Arc<RwLock<T>>,
         beacon_node: Arc<U>,
     ) -> Self {
@@ -71,7 +70,7 @@ impl<T: SlotClock, U: BeaconNode> BlockProducer<T, U> {
     }
 }
 
-impl<T: SlotClock, U: BeaconNode> BlockProducer<T, U> {
+impl<T: SlotClock, U: BeaconNode, V: DutiesReader> BlockProducer<T, U, V> {
     /// "Poll" to see if the validator is required to take any action.
     ///
     /// The slot clock will be read and any new actions undertaken.
@@ -90,13 +89,14 @@ impl<T: SlotClock, U: BeaconNode> BlockProducer<T, U> {
 
         // If this is a new slot.
         if slot > self.last_processed_slot {
-            let is_block_production_slot = {
-                let epoch_map = self.epoch_map.read().map_err(|_| Error::EpochMapPoisoned)?;
-                match epoch_map.get(&epoch) {
-                    None => return Ok(PollOutcome::ProducerDutiesUnknown(slot)),
-                    Some(duties) => duties.is_block_production_slot(slot),
-                }
-            };
+            let is_block_production_slot =
+                match self.epoch_map.is_block_production_slot(epoch, slot) {
+                    Ok(result) => result,
+                    Err(DutiesReaderError::UnknownEpoch) => {
+                        return Ok(PollOutcome::ProducerDutiesUnknown(slot))
+                    }
+                    Err(DutiesReaderError::Poisoned) => return Err(Error::EpochMapPoisoned),
+                };
 
             if is_block_production_slot {
                 self.last_processed_slot = slot;
@@ -178,6 +178,7 @@ mod tests {
     use super::test_node::TestBeaconNode;
     use super::*;
     use crate::duties::EpochDuties;
+    use crate::duties::EpochDutiesMap;
     use slot_clock::TestingSlotClock;
     use types::test_utils::{SeedableRng, TestRandom, XorShiftRng};
 
@@ -191,7 +192,7 @@ mod tests {
         let mut rng = XorShiftRng::from_seed([42; 16]);
 
         let spec = Arc::new(ChainSpec::foundation());
-        let epoch_map = Arc::new(RwLock::new(EpochDutiesMap::new()));
+        let epoch_map = Arc::new(EpochDutiesMap::new());
         let slot_clock = Arc::new(RwLock::new(TestingSlotClock::new(0)));
         let beacon_node = Arc::new(TestBeaconNode::default());
 
@@ -213,7 +214,7 @@ mod tests {
             ..std::default::Default::default()
         };
         let produce_epoch = produce_slot / spec.epoch_length;
-        epoch_map.write().unwrap().insert(produce_epoch, duties);
+        epoch_map.insert(produce_epoch, duties);
 
         // One slot before production slot...
         slot_clock.write().unwrap().set_slot(produce_slot - 1);
diff --git a/validator_client/src/block_producer/service.rs b/validator_client/src/block_producer/service.rs
index ffdb330293..822df76c1e 100644
--- a/validator_client/src/block_producer/service.rs
+++ b/validator_client/src/block_producer/service.rs
@@ -1,15 +1,15 @@
-use super::traits::BeaconNode;
+use super::traits::{BeaconNode, DutiesReader};
 use super::{BlockProducer, PollOutcome as BlockProducerPollOutcome, SlotClock};
 use slog::{error, info, warn, Logger};
 use std::time::Duration;
 
-pub struct BlockProducerService<T: SlotClock, U: BeaconNode> {
-    pub block_producer: BlockProducer<T, U>,
+pub struct BlockProducerService<T: SlotClock, U: BeaconNode, V: DutiesReader> {
+    pub block_producer: BlockProducer<T, U, V>,
     pub poll_interval_millis: u64,
     pub log: Logger,
 }
 
-impl<T: SlotClock, U: BeaconNode> BlockProducerService<T, U> {
+impl<T: SlotClock, U: BeaconNode, V: DutiesReader> BlockProducerService<T, U, V> {
     /// Run a loop which polls the block producer each `poll_interval_millis` millseconds.
     ///
     /// Logs the results of the polls.
diff --git a/validator_client/src/block_producer/traits.rs b/validator_client/src/block_producer/traits.rs
index be1c73bda5..e16af24606 100644
--- a/validator_client/src/block_producer/traits.rs
+++ b/validator_client/src/block_producer/traits.rs
@@ -17,3 +17,12 @@ pub trait BeaconNode: Send + Sync {
     /// Returns `true` if the publish was sucessful.
     fn publish_beacon_block(&self, block: BeaconBlock) -> Result<bool, BeaconNodeError>;
 }
+
+pub enum DutiesReaderError {
+    UnknownEpoch,
+    Poisoned,
+}
+
+pub trait DutiesReader: Send + Sync {
+    fn is_block_production_slot(&self, epoch: u64, slot: u64) -> Result<bool, DutiesReaderError>;
+}
diff --git a/validator_client/src/duties/mod.rs b/validator_client/src/duties/mod.rs
index 4656715bae..8e70195333 100644
--- a/validator_client/src/duties/mod.rs
+++ b/validator_client/src/duties/mod.rs
@@ -5,6 +5,7 @@ mod test_node;
 mod traits;
 
 use self::traits::{BeaconNode, BeaconNodeError};
+use super::block_producer::traits::{DutiesReader, DutiesReaderError};
 use bls::PublicKey;
 use slot_clock::SlotClock;
 use spec::ChainSpec;
@@ -36,8 +37,52 @@ impl EpochDuties {
     }
 }
 
+pub enum EpochDutiesMapError {
+    Poisoned,
+}
+
 /// Maps an `epoch` to some `EpochDuties` for a single validator.
-pub type EpochDutiesMap = HashMap<u64, EpochDuties>;
+pub struct EpochDutiesMap {
+    pub map: RwLock<HashMap<u64, EpochDuties>>,
+}
+
+impl EpochDutiesMap {
+    pub fn new() -> Self {
+        Self {
+            map: RwLock::new(HashMap::new()),
+        }
+    }
+
+    pub fn get(&self, epoch: u64) -> Result<Option<EpochDuties>, EpochDutiesMapError> {
+        let map = self.map.read().map_err(|_| EpochDutiesMapError::Poisoned)?;
+        match map.get(&epoch) {
+            Some(duties) => Ok(Some(duties.clone())),
+            None => Ok(None),
+        }
+    }
+
+    pub fn insert(
+        &self,
+        epoch: u64,
+        epoch_duties: EpochDuties,
+    ) -> Result<Option<EpochDuties>, EpochDutiesMapError> {
+        let mut map = self
+            .map
+            .write()
+            .map_err(|_| EpochDutiesMapError::Poisoned)?;
+        Ok(map.insert(epoch, epoch_duties))
+    }
+}
+
+impl DutiesReader for EpochDutiesMap {
+    fn is_block_production_slot(&self, epoch: u64, slot: u64) -> Result<bool, DutiesReaderError> {
+        let map = self.map.read().map_err(|_| DutiesReaderError::Poisoned)?;
+        let duties = map
+            .get(&epoch)
+            .ok_or_else(|| DutiesReaderError::UnknownEpoch)?;
+        Ok(duties.is_block_production_slot(slot))
+    }
+}
 
 #[derive(Debug, PartialEq, Clone, Copy)]
 pub enum PollOutcome {
@@ -68,7 +113,7 @@ pub enum Error {
 ///
 /// There is a single `DutiesManager` per validator instance.
 pub struct DutiesManager<T: SlotClock, U: BeaconNode> {
-    pub duties_map: Arc<RwLock<EpochDutiesMap>>,
+    pub duties_map: Arc<EpochDutiesMap>,
     /// The validator's public key.
     pub pubkey: PublicKey,
     pub spec: Arc<ChainSpec>,
@@ -95,14 +140,9 @@ impl<T: SlotClock, U: BeaconNode> DutiesManager<T, U> {
             .ok_or(Error::EpochLengthIsZero)?;
 
         if let Some(duties) = self.beacon_node.request_shuffling(epoch, &self.pubkey)? {
-            let mut map = self
-                .duties_map
-                .write()
-                .map_err(|_| Error::EpochMapPoisoned)?;
-
             // If these duties were known, check to see if they're updates or identical.
-            let result = if let Some(known_duties) = map.get(&epoch) {
-                if *known_duties == duties {
+            let result = if let Some(known_duties) = self.duties_map.get(epoch)? {
+                if known_duties == duties {
                     Ok(PollOutcome::NoChange(epoch))
                 } else {
                     Ok(PollOutcome::DutiesChanged(epoch, duties))
@@ -110,7 +150,7 @@ impl<T: SlotClock, U: BeaconNode> DutiesManager<T, U> {
             } else {
                 Ok(PollOutcome::NewDuties(epoch, duties))
             };
-            map.insert(epoch, duties);
+            self.duties_map.insert(epoch, duties)?;
             result
         } else {
             Ok(PollOutcome::UnknownValidatorOrEpoch(epoch))
@@ -124,6 +164,14 @@ impl From<BeaconNodeError> for Error {
     }
 }
 
+impl From<EpochDutiesMapError> for Error {
+    fn from(e: EpochDutiesMapError) -> Error {
+        match e {
+            EpochDutiesMapError::Poisoned => Error::EpochMapPoisoned,
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::test_node::TestBeaconNode;
@@ -139,7 +187,7 @@ mod tests {
     #[test]
     pub fn polling() {
         let spec = Arc::new(ChainSpec::foundation());
-        let duties_map = Arc::new(RwLock::new(EpochDutiesMap::new()));
+        let duties_map = Arc::new(EpochDutiesMap::new());
         let keypair = Keypair::random();
         let slot_clock = Arc::new(RwLock::new(TestingSlotClock::new(0)));
         let beacon_node = Arc::new(TestBeaconNode::default());
diff --git a/validator_client/src/main.rs b/validator_client/src/main.rs
index bbbc0b4c35..c1775f8264 100644
--- a/validator_client/src/main.rs
+++ b/validator_client/src/main.rs
@@ -107,7 +107,7 @@ fn main() {
 
     for keypair in keypairs {
         info!(log, "Starting validator services"; "validator" => keypair.pk.concatenated_hex_id());
-        let duties_map = Arc::new(RwLock::new(EpochDutiesMap::new()));
+        let duties_map = Arc::new(EpochDutiesMap::new());
 
         // Spawn a new thread to maintain the validator's `EpochDuties`.
         let duties_manager_thread = {