diff --git a/Source/Vault.hpp b/Source/Vault.hpp
index d01b1e1..c33a3d7 100644
--- a/Source/Vault.hpp
+++ b/Source/Vault.hpp
@@ -569,12 +569,21 @@ namespace mvlt
         // Check it is trying to set coorect type 
         if (res.RequestedType != keyTypeIt->second)
         {
-            res.RequestedType = keyTypeIt->second;
+            res.SavedType = keyTypeIt->second;
             res.IsOperationSuccess = false;
             res.ResultCode = VaultOperationResultCode::WrongType;
             return res;
         }
 
+        // Check if it is unique key
+        if (UniqueKeys.find(key) != UniqueKeys.end())
+        {
+            res.SavedType = keyTypeIt->second;
+            res.IsOperationSuccess = false;
+            res.ResultCode = VaultOperationResultCode::TryToUpdateUniqueKey;
+            return res;
+        }
+
         // Change data in template
         RecordTemplate.SetData(key, defaultKeyValue);
 
diff --git a/Source/VaultOperationResult.cpp b/Source/VaultOperationResult.cpp
index 15cc52e..0a09f89 100644
--- a/Source/VaultOperationResult.cpp
+++ b/Source/VaultOperationResult.cpp
@@ -7,6 +7,9 @@ namespace mvlt
         switch (ResultCode)
         {
         default:
+        case VaultOperationResultCode::TryToUpdateUniqueKey:
+            return "The key is unique and you can not update it default value.";
+
         case VaultOperationResultCode::DataRecordNotValid:
             return "The record referenced by VaultRecordRef is not valid.";
 
diff --git a/Source/VaultOperationResult.h b/Source/VaultOperationResult.h
index 7d5a8c8..eef5004 100644
--- a/Source/VaultOperationResult.h
+++ b/Source/VaultOperationResult.h
@@ -16,6 +16,7 @@ namespace mvlt
     /// \brief Enum with all error handling codes
     enum class VaultOperationResultCode
     {
+        TryToUpdateUniqueKey = -7,     ///< This code is returned when trying to update default value in an unique key
         RecordAlredyInSet = -6,        ///< This code is returned when trying to add an record to the set when it is already in it
         ParentVaultNotMatch = -5,      ///< This code is returned during operations on VaultRecordSet when objects depend on different Vaults
         ParentVaultNotValid = -4,      ///< This code is returned when calling VaultRecordSet operations when the parent Vault is not valid
diff --git a/Tests/VaultUnitTest.cpp b/Tests/VaultUnitTest.cpp
index b93a333..c4dc6d7 100644
--- a/Tests/VaultUnitTest.cpp
+++ b/Tests/VaultUnitTest.cpp
@@ -63,15 +63,20 @@ void Vault_UpdateKey_Test()
 
     vlt.AddKey("A", -1);
     vlt.AddKey<std::string>("B", "none");
+    vlt.AddUniqueKey<std::size_t>("C", {[](std::size_t counter, const VaultRecordRef& vrf) -> bool { return counter; }});
 
     // Correct key update
     TEST_ASSERT(vlt.UpdateKey("A", 0).IsOperationSuccess == true, "Failed to update key");
 
     // Wrong key update
-    TEST_ASSERT(vlt.UpdateKey("C", -1).ResultCode == VaultOperationResultCode::WrongKey, "Cannot update not existing key");
+    TEST_ASSERT(vlt.UpdateKey("D", -1).ResultCode == VaultOperationResultCode::WrongKey, "Cannot update not existing key");
 
     // Wrong key type
     TEST_ASSERT(vlt.UpdateKey("B", -1).ResultCode == VaultOperationResultCode::WrongType, "Cannot set incorrect type to new key value");
+
+    // Try to update unique key
+    VaultOperationResult vrs = vlt.UpdateKey<std::size_t>("C", 250);
+    TEST_ASSERT(vrs.ResultCode == VaultOperationResultCode::TryToUpdateUniqueKey, "Cannot update unique key");
 }
 
 void Vault_IsKeyExist_Test()