Java code gen "incompatible types" generic list value

I am getting an error in java code gen for a map of String->String[] in java.

The swagger source definition:

DataMap:
  description: Provides a generic map of string->string
  additionalProperties:
    $ref: '#/components/schemas/StringArray'
  title: DataMap
  type: object
StringArray:
  description: String array
  items:
    type: string
  title: StringArray
  type: array

 Results in java code:

private Map<String, List<String>> dataMap = null;

  public RequestMetaData putDataMapItem(String key, List<String> dataMapItem) {

    if (this.dataMap == null) {

      this.dataMap = new HashMap<String, List>();

    }

    this.dataMap.put(key, dataMapItem);

    return this;

  }

This does not compile.  It fails with 

error: incompatible types: HashMap<String,List> cannot be converted to Map<String,List<String>>

This seems like a common definition structure.  Has anyone seen this/resolved it?