diff --git a/pir/hashing/cuckoo_hash_table.cc b/pir/hashing/cuckoo_hash_table.cc
index 4a81655..14f7f9e 100644
--- a/pir/hashing/cuckoo_hash_table.cc
+++ b/pir/hashing/cuckoo_hash_table.cc
@@ -32,7 +32,7 @@ namespace distributed_point_functions {
 
 CuckooHashTable::CuckooHashTable(std::vector<HashFunction> hash_functions,
                                  int num_buckets, int max_relocations,
-                                 absl::optional<int> max_stash_size)
+                                 std::optional<int> max_stash_size)
     : num_buckets_(num_buckets),
       max_relocations_(max_relocations),
       max_stash_size_(max_stash_size),
@@ -46,7 +46,7 @@ CuckooHashTable::CuckooHashTable(std::vector<HashFunction> hash_functions,
 
 absl::StatusOr<std::unique_ptr<CuckooHashTable>> CuckooHashTable::Create(
     std::vector<HashFunction> hash_functions, int num_buckets,
-    int max_relocations, absl::optional<int> max_stash_size) {
+    int max_relocations, std::optional<int> max_stash_size) {
   if (num_buckets <= 0) {
     return absl::InvalidArgumentError("num_buckets must be positive");
   }
diff --git a/pir/hashing/multiple_choice_hash_table.cc b/pir/hashing/multiple_choice_hash_table.cc
index e936a8a..b9c02b6 100644
--- a/pir/hashing/multiple_choice_hash_table.cc
+++ b/pir/hashing/multiple_choice_hash_table.cc
@@ -31,7 +31,7 @@ namespace distributed_point_functions {
 absl::StatusOr<std::unique_ptr<MultipleChoiceHashTable>>
 MultipleChoiceHashTable::Create(std::vector<HashFunction> hash_functions,
                                 int num_buckets,
-                                absl::optional<int> max_bucket_size) {
+                                std::optional<int> max_bucket_size) {
   if (num_buckets <= 0) {
     return absl::InvalidArgumentError("num_buckets must be positive");
   }
@@ -48,7 +48,7 @@ MultipleChoiceHashTable::Create(std::vector<HashFunction> hash_functions,
 
 MultipleChoiceHashTable::MultipleChoiceHashTable(
     std::vector<HashFunction> hash_functions, int num_buckets,
-    absl::optional<int> max_bucket_size)
+    std::optional<int> max_bucket_size)
     : num_buckets_(num_buckets),
       max_bucket_size_(max_bucket_size),
       hash_functions_(std::move(hash_functions)),
diff --git a/pir/hashing/simple_hash_table.cc b/pir/hashing/simple_hash_table.cc
index b03c19e..caf9e79 100644
--- a/pir/hashing/simple_hash_table.cc
+++ b/pir/hashing/simple_hash_table.cc
@@ -30,7 +30,7 @@ namespace distributed_point_functions {
 
 absl::StatusOr<std::unique_ptr<SimpleHashTable>> SimpleHashTable::Create(
     std::vector<HashFunction> hash_functions, int num_buckets,
-    absl::optional<int> max_bucket_size) {
+    std::optional<int> max_bucket_size) {
   if (num_buckets <= 0) {
     return absl::InvalidArgumentError("num_buckets must be positive");
   }
@@ -46,7 +46,7 @@ absl::StatusOr<std::unique_ptr<SimpleHashTable>> SimpleHashTable::Create(
 
 SimpleHashTable::SimpleHashTable(std::vector<HashFunction> hash_functions,
                                  int num_buckets,
-                                 absl::optional<int> max_bucket_size)
+                                 std::optional<int> max_bucket_size)
     : num_buckets_(num_buckets),
       max_bucket_size_(max_bucket_size),
       hash_functions_(std::move(hash_functions)),