diff --git a/pir/cuckoo_hashed_dpf_pir_database.cc b/pir/cuckoo_hashed_dpf_pir_database.cc
index 8331377..ccfe417 100644
--- a/pir/cuckoo_hashed_dpf_pir_database.cc
+++ b/pir/cuckoo_hashed_dpf_pir_database.cc
@@ -151,7 +151,7 @@ CuckooHashedDpfPirDatabase::Builder::Build() {
 
   // For each key in the cuckoo hash table, insert it into key_database_ and
   // the corresponding value into value_database_.
-  absl::Span<const absl::optional<std::string>> cuckoo_table =
+  absl::Span<const std::optional<std::string>> cuckoo_table =
       cuckoo_hasher->GetTable();
   for (int i = 0; i < cuckoo_table.size(); ++i) {
     if (cuckoo_table[i].has_value()) {
diff --git a/pir/cuckoo_hashing_sparse_dpf_pir_client.cc b/pir/cuckoo_hashing_sparse_dpf_pir_client.cc
index 9ed0d3b..e4aca45 100644
--- a/pir/cuckoo_hashing_sparse_dpf_pir_client.cc
+++ b/pir/cuckoo_hashing_sparse_dpf_pir_client.cc
@@ -164,7 +164,7 @@ CuckooHashingSparseDpfPirClient::CreatePlainRequests(
                          std::move(request_client_state));
 }
 
-absl::StatusOr<std::vector<absl::optional<std::string>>>
+absl::StatusOr<std::vector<std::optional<std::string>>>
 CuckooHashingSparseDpfPirClient::HandleResponse(
     const PirResponse& pir_response,
     const PirRequestClientState& request_client_state) const {
@@ -199,7 +199,7 @@ CuckooHashingSparseDpfPirClient::HandleResponse(
   DPF_ASSIGN_OR_RETURN(
       std::vector<std::string> raw_responses,
       wrapped_client_->HandleResponse(pir_response, wrapped_client_state));
-  std::vector<absl::optional<std::string>> result(
+  std::vector<std::optional<std::string>> result(
       raw_responses.size() / hash_functions_.size() / 2, absl::nullopt);
   for (int i = 0; i < result.size(); ++i) {
     for (int j = 0; j < hash_functions_.size(); ++j) {
diff --git a/pir/cuckoo_hashing_sparse_dpf_pir_client_test.cc b/pir/cuckoo_hashing_sparse_dpf_pir_client_test.cc
index 2b74de6..de26c86 100644
--- a/pir/cuckoo_hashing_sparse_dpf_pir_client_test.cc
+++ b/pir/cuckoo_hashing_sparse_dpf_pir_client_test.cc
@@ -222,7 +222,7 @@ TEST_F(CuckooHashingSparseDpfPirClientTest, EndToEndSucceeds) {
                            client_->CreateRequest(queries));
   DPF_ASSERT_OK_AND_ASSIGN(PirResponse response,
                            leader_->HandleRequest(request));
-  DPF_ASSERT_OK_AND_ASSIGN(std::vector<absl::optional<std::string>> result,
+  DPF_ASSERT_OK_AND_ASSIGN(std::vector<std::optional<std::string>> result,
                            client_->HandleResponse(response, client_state));
 
   EXPECT_EQ(result.size(), queries.size());
@@ -247,7 +247,7 @@ TEST_F(CuckooHashingSparseDpfPirClientTest,
 
   DPF_ASSERT_OK_AND_ASSIGN(PirResponse response,
                            leader_->HandleRequest(request));
-  DPF_ASSERT_OK_AND_ASSIGN(std::vector<absl::optional<std::string>> result,
+  DPF_ASSERT_OK_AND_ASSIGN(std::vector<std::optional<std::string>> result,
                            client_->HandleResponse(response, client_state));
 
   EXPECT_EQ(result.size(), queries.size());