Populate ComboBox With Named Range

I use


Set rnData = ActiveSheet. Range("ProductList")
vaData = rnData.Value

With Me.model
.Clear
.List = vaData
.ListIndex = -1
End With

to populate a combobox list. 'ProductList' is a Dynamic Named Range with the definition

=OFFSET(Stock_List!$L$2,0,0, COUNTA(Stock_List!$L:$L)-1,1)

The '-1' allows for a heading at the top of the column.
This works fine when the list in col. L has more than one entry under the heading. But with only one entry I get 'Runtime error 381 - Could not set the List property, Invalid property array index' and the debug highlights on


.list=vaData