diff --git a/XenModel/XenAPI-Extensions/Host.cs b/XenModel/XenAPI-Extensions/Host.cs
index 1457bdbe7..d3b56a127 100644
--- a/XenModel/XenAPI-Extensions/Host.cs
+++ b/XenModel/XenAPI-Extensions/Host.cs
@@ -1137,7 +1137,7 @@ namespace XenAPI
                 if (Connection == null)
                     return null;
 
-                if (Helpers.DundeePlusOrGreater(Connection))
+                if (!Helper.IsNullOrEmptyOpaqueRef(control_domain))
                     return Connection.Resolve(control_domain);
 
                 var vms = Connection.ResolveAll(resident_VMs);
@@ -1166,7 +1166,7 @@ namespace XenAPI
 
                 var vms = Connection.ResolveAll(resident_VMs);
 
-                if (Helpers.DundeePlusOrGreater(Connection))
+                if (!Helper.IsNullOrEmptyOpaqueRef(control_domain))
                     return vms.Where(v => v.is_control_domain && v.opaque_ref != control_domain);
 
                 return vms.Where(v => v.is_control_domain && v.domid != 0);
diff --git a/XenModel/XenAPI-Extensions/VM.cs b/XenModel/XenAPI-Extensions/VM.cs
index 3b3fd9219..f7345d3c7 100644
--- a/XenModel/XenAPI-Extensions/VM.cs
+++ b/XenModel/XenAPI-Extensions/VM.cs
@@ -1490,7 +1490,7 @@ namespace XenAPI
                 if (host == null)
                     return false;
 
-                if (Helpers.DundeePlusOrGreater(Connection))
+                if (!Helper.IsNullOrEmptyOpaqueRef(host.control_domain))
                     return host.control_domain == opaque_ref;
 
                 var vms = Connection.ResolveAll(host.resident_VMs);