diff --git a/flake.lock b/flake.lock
index aecdf32..812f17b 100644
--- a/flake.lock
+++ b/flake.lock
@@ -2716,17 +2716,17 @@
         "rust-rapidsnark": "rust-rapidsnark"
       },
       "locked": {
-        "lastModified": 1785414238,
-        "narHash": "sha256-SNo5ZvmzB39HMgY+f0a93XoNA92e/T5Ki9Gho62COWY=",
+        "lastModified": 1785659324,
+        "narHash": "sha256-xtC9Qksgp3f3ZEDdhLuM0DegelFl4EW20jqSmhqHeHQ=",
         "owner": "logos-blockchain",
         "repo": "logos-execution-zone",
-        "rev": "f58cde1a2251c20cf418a561ad974a8c64ab2393",
+        "rev": "15144ddb8437f48cdce32908e122dbb7eea68399",
         "type": "github"
       },
       "original": {
         "owner": "logos-blockchain",
+        "ref": "v0.2.1",
         "repo": "logos-execution-zone",
-        "rev": "f58cde1a2251c20cf418a561ad974a8c64ab2393",
         "type": "github"
       }
     },
diff --git a/flake.nix b/flake.nix
index 529e992..0aeb25f 100644
--- a/flake.nix
+++ b/flake.nix
@@ -4,7 +4,7 @@
   inputs = {
     logos-module-builder.url = "github:logos-co/logos-module-builder";
     nix-bundle-lgx.url = "github:logos-co/nix-bundle-lgx";
-    logos-execution-zone.url = "github:logos-blockchain/logos-execution-zone?rev=f58cde1a2251c20cf418a561ad974a8c64ab2393";
+    logos-execution-zone.url = "github:logos-blockchain/logos-execution-zone?ref=v0.2.1";
   };
 
   outputs = inputs@{ logos-module-builder, ... }:
diff --git a/src/lez_core_module.cpp b/src/lez_core_module.cpp
index 11a6bc3..9e88398 100644
--- a/src/lez_core_module.cpp
+++ b/src/lez_core_module.cpp
@@ -212,28 +212,31 @@ bool jsonToFfiPrivateAccountKeys(const std::string& json, FfiPrivateAccountKeys*
     if (doc.is_discarded() || !doc.is_object())
         return false;
 
-    if (doc.contains(JsonKeys::NullifierPublicKey) && doc[JsonKeys::NullifierPublicKey].is_string()) {
-        if (!hexToBytes32(doc[JsonKeys::NullifierPublicKey].get<std::string>(), &output_keys->nullifier_public_key))
-            return false;
-    }
+    // Nullifier public key is mandatory: a missing/wrong-typed value must not fall back to zero.
+    if (!doc.contains(JsonKeys::NullifierPublicKey) || !doc[JsonKeys::NullifierPublicKey].is_string())
+        return false;
+    if (!hexToBytes32(doc[JsonKeys::NullifierPublicKey].get<std::string>(), &output_keys->nullifier_public_key))
+        return false;
+
+    output_keys->viewing_public_key = nullptr;
+    output_keys->viewing_public_key_len = 0;
+
+    if (doc.contains(JsonKeys::ViewingPublicKey)) {
+        if (!doc[JsonKeys::ViewingPublicKey].is_string())
+            return false;
 
-    if (doc.contains(JsonKeys::ViewingPublicKey) && doc[JsonKeys::ViewingPublicKey].is_string()) {
         std::vector<uint8_t> buffer;
         if (!hexToBytes(doc[JsonKeys::ViewingPublicKey].get<std::string>(), buffer))
             return false;
 
-        if (buffer.empty()) {
-            output_keys->viewing_public_key = nullptr;
-            output_keys->viewing_public_key_len = 0;
-        } else {
+        if (!buffer.empty()) {
             auto* data = static_cast<uint8_t*>(malloc(buffer.size()));
+            if (!data)
+                return false;
             memcpy(data, buffer.data(), buffer.size());
             output_keys->viewing_public_key = data;
             output_keys->viewing_public_key_len = buffer.size();
         }
-    } else {
-        output_keys->viewing_public_key = nullptr;
-        output_keys->viewing_public_key_len = 0;
     }
 
     return true;
diff --git a/tests/test_lez_core.cpp b/tests/test_lez_core.cpp
index bb072f1..3af98ef 100644
--- a/tests/test_lez_core.cpp
+++ b/tests/test_lez_core.cpp
@@ -288,6 +288,68 @@ LOGOS_TEST(transfer_shielded_invalid_keys_json_error) {
     LOGOS_ASSERT_FALSE(t.cFunctionCalled("wallet_ffi_transfer_shielded"));
 }
 
+// A missing nullifier_public_key must not succeed with a zero key.
+LOGOS_TEST(transfer_shielded_missing_nullifier_key_error) {
+    auto t = LogosTestContext("logos_execution_zone");
+    LEZCoreModule module;
+
+    const nlohmann::json obj = parseObject(module.transfer_shielded(VALID_ID, "{}", VALID_U128));
+    LOGOS_ASSERT_FALSE(obj["success"].get<bool>());
+    LOGOS_ASSERT_FALSE(t.cFunctionCalled("wallet_ffi_transfer_shielded"));
+}
+
+LOGOS_TEST(transfer_shielded_misspelled_nullifier_key_error) {
+    auto t = LogosTestContext("logos_execution_zone");
+    LEZCoreModule module;
+
+    const std::string keysJson = std::string("{\"nullifierPublicKey\":\"") + std::string(64, 'a') + "\"}";
+    const nlohmann::json obj = parseObject(module.transfer_shielded(VALID_ID, keysJson, VALID_U128));
+    LOGOS_ASSERT_FALSE(obj["success"].get<bool>());
+    LOGOS_ASSERT_FALSE(t.cFunctionCalled("wallet_ffi_transfer_shielded"));
+}
+
+LOGOS_TEST(transfer_shielded_abbreviated_nullifier_key_error) {
+    auto t = LogosTestContext("logos_execution_zone");
+    LEZCoreModule module;
+
+    const std::string keysJson = std::string("{\"nullifier_pubkey\":\"") + std::string(64, 'a') + "\"}";
+    const nlohmann::json obj = parseObject(module.transfer_shielded(VALID_ID, keysJson, VALID_U128));
+    LOGOS_ASSERT_FALSE(obj["success"].get<bool>());
+    LOGOS_ASSERT_FALSE(t.cFunctionCalled("wallet_ffi_transfer_shielded"));
+}
+
+LOGOS_TEST(transfer_shielded_nullifier_key_omitted_viewing_key_only_error) {
+    auto t = LogosTestContext("logos_execution_zone");
+    LEZCoreModule module;
+
+    const std::string keysJson = std::string("{\"viewing_public_key\":\"") + std::string(64, 'a') + "\"}";
+    const nlohmann::json obj = parseObject(module.transfer_shielded(VALID_ID, keysJson, VALID_U128));
+    LOGOS_ASSERT_FALSE(obj["success"].get<bool>());
+    LOGOS_ASSERT_FALSE(t.cFunctionCalled("wallet_ffi_transfer_shielded"));
+}
+
+LOGOS_TEST(transfer_shielded_nullifier_key_wrong_type_error) {
+    auto t = LogosTestContext("logos_execution_zone");
+    LEZCoreModule module;
+
+    const std::string keysJson = "{\"nullifier_public_key\": 12345}";
+    const nlohmann::json obj = parseObject(module.transfer_shielded(VALID_ID, keysJson, VALID_U128));
+    LOGOS_ASSERT_FALSE(obj["success"].get<bool>());
+    LOGOS_ASSERT_FALSE(t.cFunctionCalled("wallet_ffi_transfer_shielded"));
+}
+
+// A non-string viewing_public_key must be rejected, not treated as absent.
+LOGOS_TEST(transfer_shielded_viewing_key_wrong_type_error) {
+    auto t = LogosTestContext("logos_execution_zone");
+    LEZCoreModule module;
+
+    const std::string keysJson = std::string("{\"nullifier_public_key\":\"") + std::string(64, 'a')
+        + "\",\"viewing_public_key\": 12345}";
+    const nlohmann::json obj = parseObject(module.transfer_shielded(VALID_ID, keysJson, VALID_U128));
+    LOGOS_ASSERT_FALSE(obj["success"].get<bool>());
+    LOGOS_ASSERT_FALSE(t.cFunctionCalled("wallet_ffi_transfer_shielded"));
+}
+
 LOGOS_TEST(transfer_shielded_success_json) {
     auto t = LogosTestContext("logos_execution_zone");
     LEZCoreModule module;
@@ -335,6 +397,16 @@ LOGOS_TEST(transfer_shielded_without_identifier_uses_random_nonzero_identifier)
     LOGOS_ASSERT_FALSE(memcmp(first, second, sizeof(first)) == 0);
 }
 
+// transfer_private shares the same parser, so it must reject a missing key too.
+LOGOS_TEST(transfer_private_missing_nullifier_key_error) {
+    auto t = LogosTestContext("logos_execution_zone");
+    LEZCoreModule module;
+
+    const nlohmann::json obj = parseObject(module.transfer_private(VALID_ID, "{}", VALID_U128));
+    LOGOS_ASSERT_FALSE(obj["success"].get<bool>());
+    LOGOS_ASSERT_FALSE(t.cFunctionCalled("wallet_ffi_transfer_private"));
+}
+
 // transfer_private mirrors transfer_shielded's identifier handling exactly (see above).
 LOGOS_TEST(transfer_private_with_identifier_forwards_it_unchanged) {
     auto t = LogosTestContext("logos_execution_zone");