diff --git a/quiche/oblivious_http/buffers/oblivious_http_response_test.cc b/quiche/oblivious_http/buffers/oblivious_http_response_test.cc
index 4178c73..4ff5f50 100644
--- a/quiche/oblivious_http/buffers/oblivious_http_response_test.cc
+++ b/quiche/oblivious_http/buffers/oblivious_http_response_test.cc
@@ -23,25 +23,34 @@
 std::string GetHpkePrivateKey() {
   absl::string_view hpke_key_hex =
       "b77431ecfa8f4cfc30d6e467aafa06944dffe28cb9dd1409e33a3045f5adc8a1";
-  return absl::HexStringToBytes(hpke_key_hex);
+  std::string hpke_key_bytes;
+  EXPECT_TRUE(absl::HexStringToBytes(hpke_key_hex, &hpke_key_bytes));
+  return hpke_key_bytes;
 }
 
 std::string GetHpkePublicKey() {
   absl::string_view public_key =
       "6d21cfe09fbea5122f9ebc2eb2a69fcc4f06408cd54aac934f012e76fcdcef62";
-  return absl::HexStringToBytes(public_key);
+  std::string public_key_bytes;
+  EXPECT_TRUE(absl::HexStringToBytes(public_key, &public_key_bytes));
+  return public_key_bytes;
 }
 
 std::string GetSeed() {
   absl::string_view seed =
       "52c4a758a802cd8b936eceea314432798d5baf2d7e9235dc084ab1b9cfa2f736";
-  return absl::HexStringToBytes(seed);
+  std::string seed_bytes;
+  EXPECT_TRUE(absl::HexStringToBytes(seed, &seed_bytes));
+  return seed_bytes;
 }
 
 std::string GetSeededEncapsulatedKey() {
   absl::string_view encapsulated_key =
       "37fda3567bdbd628e88668c3c8d7e97d1d1253b6d4ea6d44c150f741f1bf4431";
-  return absl::HexStringToBytes(encapsulated_key);
+  std::string encapsulated_key_bytes;
+  EXPECT_TRUE(
+      absl::HexStringToBytes(encapsulated_key, &encapsulated_key_bytes));
+  return encapsulated_key_bytes;
 }
 
 const ObliviousHttpHeaderKeyConfig GetOhttpKeyConfig(uint8_t key_id,
@@ -151,13 +160,16 @@
   absl::string_view encrypted_response =
       "39d5b03c02c97e216df444e4681007105974d4df1585aae05e7b53f3ccdb55d51f711d48"
       "eeefbc1a555d6d928e35df33fd23c23846fa7b083e30692f7b";
+  std::string encrypted_response_bytes;
+  ASSERT_TRUE(
+      absl::HexStringToBytes(encrypted_response, &encrypted_response_bytes));
   auto oblivious_context =
       SetUpObliviousHttpContext(4, EVP_HPKE_DHKEM_X25519_HKDF_SHA256,
                                 EVP_HPKE_HKDF_SHA256, EVP_HPKE_AES_256_GCM,
                                 "test")
           .ReleaseContext();
   auto decapsulated = ObliviousHttpResponse::CreateClientObliviousResponse(
-      absl::HexStringToBytes(encrypted_response), oblivious_context);
+      std::move(encrypted_response_bytes), oblivious_context);
   EXPECT_TRUE(decapsulated.ok());
   auto decrypted = decapsulated->GetPlaintextData();
   EXPECT_EQ(decrypted, "test response");
@@ -203,10 +215,13 @@
                 'z'));
   absl::string_view expected_encrypted_response =
       "2a3271ac4e6a501f51d0264d3dd7d0bc8a06973b58e89c26d6dac06144";
+  std::string expected_encrypted_response_bytes;
+  ASSERT_TRUE(absl::HexStringToBytes(expected_encrypted_response,
+                                     &expected_encrypted_response_bytes));
   EXPECT_EQ(
       server_response_encapsulate->EncapsulateAndSerialize().substr(
           GetResponseNonceLength(*(server_request_context.hpke_context_))),
-      absl::HexStringToBytes(expected_encrypted_response));
+      expected_encrypted_response_bytes);
 }
 
 }  // namespace quiche
diff --git a/quiche/oblivious_http/common/oblivious_http_header_key_config_test.cc b/quiche/oblivious_http/common/oblivious_http_header_key_config_test.cc
index f9a8348..40d8cf4 100644
--- a/quiche/oblivious_http/common/oblivious_http_header_key_config_test.cc
+++ b/quiche/oblivious_http/common/oblivious_http_header_key_config_test.cc
@@ -191,11 +191,13 @@
 }
 
 TEST(ObliviousHttpKeyConfigs, TwoSimilarKeyConfigs) {
-  std::string key = absl::HexStringToBytes(
+  std::string key;
+  ASSERT_TRUE(absl::HexStringToBytes(
       "4b0020f83e0a17cbdb18d2684dd2a9b087a43e5f3fa3fa27a049bc746a6e97a1e0244b00"
       "0400010002"  // Intentional concatenation
       "4f0020f83e0a17cbdb18d2684dd2a9b087a43e5f3fa3fa27a049bc746a6e97a1e0244b00"
-      "0400010001");
+      "0400010001",
+      &key));
   EXPECT_THAT(ObliviousHttpKeyConfigs::ParseConcatenatedKeys(key).value(),
               Property(&ObliviousHttpKeyConfigs::NumKeys, 2));
   EXPECT_THAT(
@@ -205,27 +207,34 @@
 }
 
 TEST(ObliviousHttpKeyConfigs, RFCExample) {
-  std::string key = absl::HexStringToBytes(
+  std::string key;
+  ASSERT_TRUE(absl::HexStringToBytes(
       "01002031e1f05a740102115220e9af918f738674aec95f54db6e04eb705aae8e79815500"
-      "080001000100010003");
+      "080001000100010003",
+      &key));
   auto configs = ObliviousHttpKeyConfigs::ParseConcatenatedKeys(key).value();
   EXPECT_THAT(configs, Property(&ObliviousHttpKeyConfigs::NumKeys, 1));
   EXPECT_THAT(
       configs.PreferredConfig(),
       AllOf(HasKeyId(0x01), HasKemId(EVP_HPKE_DHKEM_X25519_HKDF_SHA256),
             HasKdfId(EVP_HPKE_HKDF_SHA256), HasAeadId(EVP_HPKE_AES_128_GCM)));
+  std::string expected_public_key;
+  ASSERT_TRUE(absl::HexStringToBytes(
+      "31e1f05a740102115220e9af918f738674aec95f54db6e04eb705aae8e798155",
+      &expected_public_key));
   EXPECT_THAT(
       configs.GetPublicKeyForId(configs.PreferredConfig().GetKeyId()).value(),
-      StrEq(absl::HexStringToBytes(
-          "31e1f05a740102115220e9af918f738674aec95f54db6e04eb705aae8e798155")));
+      StrEq(expected_public_key));
 }
 
 TEST(ObliviousHttpKeyConfigs, DuplicateKeyId) {
-  std::string key = absl::HexStringToBytes(
+  std::string key;
+  ASSERT_TRUE(absl::HexStringToBytes(
       "4b0020f83e0a17cbdb18d2684dd2a9b087a43e5f3fa3fa27a049bc746a6e97a1e0244b00"
       "0400010002"  // Intentional concatenation
       "4b0020f83e0a17cbdb18d2684dd2a9b087a43e5f3fa3fb27a049bc746a6e97a1e0244b00"
-      "0400010001");
+      "0400010001",
+      &key));
   EXPECT_FALSE(ObliviousHttpKeyConfigs::ParseConcatenatedKeys(key).ok());
 }