diff --git a/runtime/src/bank.rs b/runtime/src/bank.rs
index 0ee8b088ea..d3454394db 100644
--- a/runtime/src/bank.rs
+++ b/runtime/src/bank.rs
@@ -4,7 +4,7 @@
 //! already been signed and verified.
 
 use crate::accounts::{Accounts, ErrorCounters, InstructionAccounts, InstructionLoaders};
-use crate::hash_queue::HashQueue;
+use crate::blockhash_queue::BlockhashQueue;
 use crate::runtime;
 use crate::status_cache::StatusCache;
 use bincode::serialize;
@@ -121,7 +121,7 @@ pub struct Bank {
     status_cache: RwLock<BankStatusCache>,
 
     /// FIFO queue of `recent_blockhash` items
-    blockhash_queue: RwLock<HashQueue>,
+    blockhash_queue: RwLock<BlockhashQueue>,
 
     /// Previous checkpoint of this bank
     parent: RwLock<Option<Arc<Bank>>>,
@@ -156,7 +156,7 @@ pub struct Bank {
     is_delta: AtomicBool,
 }
 
-impl Default for HashQueue {
+impl Default for BlockhashQueue {
     fn default() -> Self {
         Self::new(MAX_RECENT_BLOCKHASHES)
     }
@@ -475,7 +475,7 @@ impl Bank {
         txs.iter()
             .zip(lock_results.into_iter())
             .map(|(tx, lock_res)| {
-                if lock_res.is_ok() && !hash_queue.check_entry_age(tx.recent_blockhash, max_age) {
+                if lock_res.is_ok() && !hash_queue.check_hash_age(tx.recent_blockhash, max_age) {
                     error_counters.reserve_blockhash += 1;
                     Err(TransactionError::BlockhashNotFound)
                 } else {
diff --git a/runtime/src/blockhash_queue.rs b/runtime/src/blockhash_queue.rs
new file mode 100644
index 0000000000..d366819a99
--- /dev/null
+++ b/runtime/src/blockhash_queue.rs
@@ -0,0 +1,139 @@
+use hashbrown::HashMap;
+use solana_sdk::hash::Hash;
+use solana_sdk::timing::timestamp;
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+struct HashAge {
+    timestamp: u64,
+    hash_height: u64,
+}
+
+/// Low memory overhead, so can be cloned for every checkpoint
+#[derive(Clone)]
+pub struct BlockhashQueue {
+    /// updated whenever an hash is registered
+    hash_height: u64,
+
+    /// last hash to be registered
+    last_hash: Option<Hash>,
+
+    ages: HashMap<Hash, HashAge>,
+
+    /// hashes older than `max_age` will be dropped from the queue
+    max_age: usize,
+}
+
+impl BlockhashQueue {
+    pub fn new(max_age: usize) -> Self {
+        Self {
+            ages: HashMap::new(),
+            hash_height: 0,
+            last_hash: None,
+            max_age,
+        }
+    }
+
+    #[allow(dead_code)]
+    pub fn hash_height(&self) -> u64 {
+        self.hash_height
+    }
+
+    pub fn last_hash(&self) -> Hash {
+        self.last_hash.expect("no hash has been set")
+    }
+
+    /// Check if the age of the hash is within the max_age
+    /// return false for any hashes with an age above max_age
+    pub fn check_hash_age(&self, hash: Hash, max_age: usize) -> bool {
+        let hash_age = self.ages.get(&hash);
+        match hash_age {
+            Some(age) => self.hash_height - age.hash_height <= max_age as u64,
+            _ => false,
+        }
+    }
+    /// check if hash is valid
+    #[cfg(test)]
+    pub fn check_hash(&self, hash: Hash) -> bool {
+        self.ages.get(&hash).is_some()
+    }
+
+    pub fn genesis_hash(&mut self, hash: &Hash) {
+        self.ages.insert(
+            *hash,
+            HashAge {
+                hash_height: 0,
+                timestamp: timestamp(),
+            },
+        );
+
+        self.last_hash = Some(*hash);
+    }
+
+    pub fn register_hash(&mut self, hash: &Hash) {
+        self.hash_height += 1;
+        let hash_height = self.hash_height;
+
+        // this clean up can be deferred until sigs gets larger
+        //  because we verify age.nth every place we check for validity
+        let max_age = self.max_age;
+        if self.ages.len() >= max_age {
+            self.ages
+                .retain(|_, age| hash_height - age.hash_height <= max_age as u64);
+        }
+        self.ages.insert(
+            *hash,
+            HashAge {
+                hash_height,
+                timestamp: timestamp(),
+            },
+        );
+
+        self.last_hash = Some(*hash);
+    }
+
+    /// Maps a hash height to a timestamp
+    pub fn hash_height_to_timestamp(&self, hash_height: u64) -> Option<u64> {
+        for age in self.ages.values() {
+            if age.hash_height == hash_height {
+                return Some(age.timestamp);
+            }
+        }
+        None
+    }
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use bincode::serialize;
+    use solana_sdk::hash::hash;
+
+    #[test]
+    fn test_register_hash() {
+        let last_hash = Hash::default();
+        let mut hash_queue = BlockhashQueue::new(100);
+        assert!(!hash_queue.check_hash(last_hash));
+        hash_queue.register_hash(&last_hash);
+        assert!(hash_queue.check_hash(last_hash));
+        assert_eq!(hash_queue.hash_height(), 1);
+    }
+    #[test]
+    fn test_reject_old_last_hash() {
+        let last_hash = Hash::default();
+        let mut hash_queue = BlockhashQueue::new(100);
+        for i in 0..100 {
+            let last_hash = hash(&serialize(&i).unwrap()); // Unique hash
+            hash_queue.register_hash(&last_hash);
+        }
+        // Assert we're no longer able to use the oldest hash.
+        assert!(!hash_queue.check_hash(last_hash));
+    }
+    /// test that when max age is 0, that a valid last_hash still passes the age check
+    #[test]
+    fn test_queue_init_blockhash() {
+        let last_hash = Hash::default();
+        let mut hash_queue = BlockhashQueue::new(100);
+        hash_queue.register_hash(&last_hash);
+        assert_eq!(last_hash, hash_queue.last_hash());
+        assert!(hash_queue.check_hash_age(last_hash, 0));
+    }
+}
diff --git a/runtime/src/hash_queue.rs b/runtime/src/hash_queue.rs
deleted file mode 100644
index 75f6dd3bdf..0000000000
--- a/runtime/src/hash_queue.rs
+++ /dev/null
@@ -1,129 +0,0 @@
-use hashbrown::HashMap;
-use solana_sdk::hash::Hash;
-use solana_sdk::timing::timestamp;
-
-#[derive(Debug, PartialEq, Eq, Clone)]
-struct HashQueueEntry {
-    timestamp: u64,
-    hash_height: u64,
-}
-
-/// Low memory overhead, so can be cloned for every checkpoint
-#[derive(Clone)]
-pub struct HashQueue {
-    /// updated whenever an hash is registered
-    hash_height: u64,
-
-    /// last hash to be registered
-    last_hash: Option<Hash>,
-
-    entries: HashMap<Hash, HashQueueEntry>,
-
-    max_entries: usize,
-}
-
-impl HashQueue {
-    pub fn new(max_entries: usize) -> Self {
-        Self {
-            entries: HashMap::new(),
-            hash_height: 0,
-            last_hash: None,
-            max_entries,
-        }
-    }
-
-    #[allow(dead_code)]
-    pub fn hash_height(&self) -> u64 {
-        self.hash_height
-    }
-
-    pub fn last_hash(&self) -> Hash {
-        self.last_hash.expect("no hash has been set")
-    }
-
-    /// Check if the age of the entry is within the max_age
-    /// return false for any entries with an age equal to or above max_age
-    pub fn check_entry_age(&self, entry: Hash, max_age: usize) -> bool {
-        let entry = self.entries.get(&entry);
-        match entry {
-            Some(entry) => self.hash_height - entry.hash_height < max_age as u64,
-            _ => false,
-        }
-    }
-    /// check if entry is valid
-    #[cfg(test)]
-    pub fn check_entry(&self, entry: Hash) -> bool {
-        self.entries.get(&entry).is_some()
-    }
-
-    pub fn genesis_hash(&mut self, hash: &Hash) {
-        self.entries.insert(
-            *hash,
-            HashQueueEntry {
-                hash_height: 0,
-                timestamp: timestamp(),
-            },
-        );
-
-        self.last_hash = Some(*hash);
-    }
-
-    pub fn register_hash(&mut self, hash: &Hash) {
-        self.hash_height += 1;
-        let hash_height = self.hash_height;
-
-        // this clean up can be deferred until sigs gets larger
-        //  because we verify entry.nth every place we check for validity
-        let max_entries = self.max_entries;
-        if self.entries.len() >= max_entries {
-            self.entries
-                .retain(|_, entry| hash_height - entry.hash_height <= max_entries as u64);
-        }
-        self.entries.insert(
-            *hash,
-            HashQueueEntry {
-                hash_height,
-                timestamp: timestamp(),
-            },
-        );
-
-        self.last_hash = Some(*hash);
-    }
-
-    /// Maps a hash height to a timestamp
-    pub fn hash_height_to_timestamp(&self, hash_height: u64) -> Option<u64> {
-        for entry in self.entries.values() {
-            if entry.hash_height == hash_height {
-                return Some(entry.timestamp);
-            }
-        }
-        None
-    }
-}
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use bincode::serialize;
-    use solana_sdk::hash::hash;
-
-    #[test]
-    fn test_register_hash() {
-        let last_hash = Hash::default();
-        let mut entry_queue = HashQueue::new(100);
-        assert!(!entry_queue.check_entry(last_hash));
-        entry_queue.register_hash(&last_hash);
-        assert!(entry_queue.check_entry(last_hash));
-        assert_eq!(entry_queue.hash_height(), 1);
-    }
-    #[test]
-    fn test_reject_old_last_hash() {
-        let last_hash = Hash::default();
-        let mut entry_queue = HashQueue::new(100);
-        for i in 0..100 {
-            let last_hash = hash(&serialize(&i).unwrap()); // Unique hash
-            entry_queue.register_hash(&last_hash);
-        }
-        // Assert we're no longer able to use the oldest entry ID.
-        assert!(!entry_queue.check_entry(last_hash));
-    }
-}
diff --git a/runtime/src/lib.rs b/runtime/src/lib.rs
index 291dc2fb87..2ce51a1f93 100644
--- a/runtime/src/lib.rs
+++ b/runtime/src/lib.rs
@@ -1,8 +1,8 @@
 mod accounts;
 pub mod append_vec;
 pub mod bank;
+mod blockhash_queue;
 pub mod bloom;
-mod hash_queue;
 pub mod loader_utils;
 mod native_loader;
 pub mod runtime;