diff --git a/src/lib/tls/tls13_pqc/hybrid_public_key.cpp b/src/lib/tls/tls13_pqc/hybrid_public_key.cpp
index dd985c31145..430b7024ab9 100644
--- a/src/lib/tls/tls13_pqc/hybrid_public_key.cpp
+++ b/src/lib/tls/tls13_pqc/hybrid_public_key.cpp
@@ -146,7 +146,7 @@ std::vector<size_t> public_value_lengths_for_group(Group_Params group) {
 std::vector<std::unique_ptr<Public_Key>> convert_kex_to_kem_pks(std::vector<std::unique_ptr<Public_Key>> pks) {
    std::vector<std::unique_ptr<Public_Key>> result;
    std::transform(pks.begin(), pks.end(), std::back_inserter(result), [](auto& key) -> std::unique_ptr<Public_Key> {
-      BOTAN_ASSERT_NONNULL(key);
+      BOTAN_ARG_CHECK(key != nullptr, "Public key list contains a nullptr");
       if(key->supports_operation(PublicKeyOperation::KeyAgreement) &&
          !key->supports_operation(PublicKeyOperation::KeyEncapsulation)) {
          return std::make_unique<KEX_to_KEM_Adapter_PublicKey>(std::move(key));
@@ -160,7 +160,7 @@ std::vector<std::unique_ptr<Public_Key>> convert_kex_to_kem_pks(std::vector<std:
 std::vector<std::unique_ptr<Private_Key>> convert_kex_to_kem_sks(std::vector<std::unique_ptr<Private_Key>> sks) {
    std::vector<std::unique_ptr<Private_Key>> result;
    std::transform(sks.begin(), sks.end(), std::back_inserter(result), [](auto& key) -> std::unique_ptr<Private_Key> {
-      BOTAN_ASSERT_NONNULL(key);
+      BOTAN_ARG_CHECK(key != nullptr, "Private key list contains a nullptr");
       if(key->supports_operation(PublicKeyOperation::KeyAgreement) &&
          !key->supports_operation(PublicKeyOperation::KeyEncapsulation)) {
          auto ka_key = dynamic_cast<PK_Key_Agreement_Key*>(key.get());