diff --git a/src/ApiService/ApiService/Functions/AgentRegistration.cs b/src/ApiService/ApiService/Functions/AgentRegistration.cs
index 526db0f723f..1f319426efa 100644
--- a/src/ApiService/ApiService/Functions/AgentRegistration.cs
+++ b/src/ApiService/ApiService/Functions/AgentRegistration.cs
@@ -110,7 +110,7 @@ private async Async.Task<HttpResponseData> Post(HttpRequestData req) {
         var version = uri["version"] ?? "1.0.0";
 
         var computerName = uri["computer_name"];
-        long? instanceId = null;
+        string? instanceId = null;
         if (computerName is not null) {
             instanceId = InstanceIds.InstanceIdFromComputerName(computerName);
         }