diff --git a/pir/simple_hashing_sparse_dpf_pir_client.cc b/pir/simple_hashing_sparse_dpf_pir_client.cc
index 33f571c..f4272e7 100644
--- a/pir/simple_hashing_sparse_dpf_pir_client.cc
+++ b/pir/simple_hashing_sparse_dpf_pir_client.cc
@@ -157,7 +157,7 @@ SimpleHashingSparseDpfPirClient::CreatePlainRequests(
                          std::move(request_client_state));
 }
 
-absl::StatusOr<std::vector<absl::optional<std::string>>>
+absl::StatusOr<std::vector<std::optional<std::string>>>
 SimpleHashingSparseDpfPirClient::HandleResponse(
     const PirResponse& pir_response,
     const PirRequestClientState& request_client_state) const {
@@ -188,8 +188,8 @@ SimpleHashingSparseDpfPirClient::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(raw_responses.size(),
-                                                  absl::nullopt);
+  std::vector<std::optional<std::string>> result(raw_responses.size(),
+                                                 absl::nullopt);
   for (int i = 0; i < result.size(); ++i) {
     // We need to use a CodedInputStream here to handle the null bytes at the
     // end of the string.
diff --git a/pir/simple_hashing_sparse_dpf_pir_client_test.cc b/pir/simple_hashing_sparse_dpf_pir_client_test.cc
index 7a10eed..7d14cbe 100644
--- a/pir/simple_hashing_sparse_dpf_pir_client_test.cc
+++ b/pir/simple_hashing_sparse_dpf_pir_client_test.cc
@@ -208,7 +208,7 @@ TEST_F(SimpleHashingSparseDpfPirClientTest, 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());
@@ -233,7 +233,7 @@ TEST_F(SimpleHashingSparseDpfPirClientTest,
 
   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());