Cannot Bind argument to Resource Key because it's an empty string

resourcekey.ps1

PSDesiredStateConfiguration\node : Cannot bind argument to parameter 'ResourceKey' because it is an empty string.
At C:\Temp\Build Hyper-V Host.ps1:15 char:5
+     node localhost
+     ~~~~
    + CategoryInfo          : InvalidData: (:) [PSDesiredStateConfiguration\node], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorEmptyStringNotAllowed,PSDesiredStateConfiguration\node
 
Update-DependsOn : Index operation failed; the array index evaluated to null.
At C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules\PSDesiredStateConfiguration\PSDesiredStateConfiguration.psm1:2208 char:17
+ ...             Update-DependsOn $Script:NodesInThisConfiguration[$mofNod ...
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [Update-DependsOn], RuntimeException
    + FullyQualifiedErrorId : NullArrayIndex,Update-DependsOn