diff --git a/consensus/types/src/beacon_state/pubkey_cache.rs b/consensus/types/src/beacon_state/pubkey_cache.rs
index d81801e77d..b789e6fc7d 100644
--- a/consensus/types/src/beacon_state/pubkey_cache.rs
+++ b/consensus/types/src/beacon_state/pubkey_cache.rs
@@ -1,16 +1,15 @@
 use crate::*;
-use serde_derive::{Deserialize, Serialize};
-use std::collections::HashMap;
+use rpds::HashTrieMapSync as HashTrieMap;
 
 type ValidatorIndex = usize;
 
-#[derive(Debug, PartialEq, Clone, Default, Serialize, Deserialize)]
+#[derive(Debug, PartialEq, Clone, Default)]
 pub struct PubkeyCache {
-    /// Maintain the number of keys added to the map. It is not sufficient to just use the HashMap
-    /// len, as it does not increase when duplicate keys are added. Duplicate keys are used during
-    /// testing.
+    /// Maintain the number of keys added to the map. It is not sufficient to just use the
+    /// HashTrieMap len, as it does not increase when duplicate keys are added. Duplicate keys are
+    /// used during testing.
     len: usize,
-    map: HashMap<PublicKeyBytes, ValidatorIndex>,
+    map: HashTrieMap<PublicKeyBytes, ValidatorIndex>,
 }
 
 impl PubkeyCache {
@@ -25,7 +24,7 @@ impl PubkeyCache {
     /// that an index is never skipped.
     pub fn insert(&mut self, pubkey: PublicKeyBytes, index: ValidatorIndex) -> bool {
         if index == self.len {
-            self.map.insert(pubkey, index);
+            self.map.insert_mut(pubkey, index);
             self.len = self
                 .len
                 .checked_add(1)