amazon web services – AWS DMS, can’t migrate CSV to DynamoDB with composite key

I’d like to migrate CSV data from an S3 bucket into a DynamoDB table. My issue is I can’t get the service to create a table with a composite (Partition Key, Sort Key) primary key, while exporting to a table with no sort key works fine.

This is the sample CSV file I’m working with:

city_name city_original_name country_code timezone feature_class
xixerella Xixerella AD Europe/Andorra PPL
vila Vila AD Europe/Andorra PPL
casas vila Vila AD Europe/Andorra PPL
tossalet i vinyals Tossalet i Vinyals AD Europe/Andorra PPLL
sornas Sornàs AD Europe/Andorra PPL
soldeu Soldeu AD Europe/Andorra PPL
sola d’encamp Solà d’Encamp AD Europe/Andorra ADMD

The following object mapping works fine, but doesn’t create a composite key, as expected:

{
  "TableCount": "1",
  "Tables": (
    {
      "TableName": "towns",
      "TablePath": "geo/towns/",
      "TableOwner": "geo",
      "TableColumns": (
        {
          "ColumnName": "City",
          "ColumnType": "STRING",
          "ColumnLength": "200",
          "ColumnNullable": "false",
          "ColumnIsPk": "true"
        },
        {
          "ColumnName": "CityLocalName",
          "ColumnType": "STRING",
          "ColumnLength": "200"
        },
...snip....

The DynamoDB console displays the table as expected: console screenshot

This one however crashes the migration task

{
  "TableCount": "1",
  "Tables": (
    {
      "TableName": "towns",
      "TablePath": "geo/towns/",
      "TableOwner": "geo",
      "TableColumns": (
        {
          "ColumnName": "City",
          "ColumnType": "STRING",
          "ColumnLength": "200",
          "ColumnNullable": "false",
          "ColumnIsPk": "true"
        },
        {
          "ColumnName": "CityLocalName",
          "ColumnType": "STRING",
          "ColumnLength": "200";
        "ColumnIsPk": "true"
        },
...snip...

The following logs are issued at the same time:

(TARGET_LOAD )I: Using source table definition to create table. Source table name is “towns” (dynamodb_table_requests.c:86)
(TARGET_LOAD )E: Table ‘towns’ has composite primary key (1025900) (dynamodb_imp.c:368)
(TARGET_LOAD )E: Unable to determine hash key for table ‘towns’ (1025900) (dynamodb_table_requests.c:399)
(TARGET_LOAD )E: Failed to initialize create table request. (1020413) (dynamodb_table_requests.c:92)

I expect to be able to export that data to table with a composite key, as defined in the previous object mapping definition. How would I fix this ?