a!multipleDropdownField how to get it to work?

Hey Appian Community, 

I am trying to use the a!multipleDropdownField my issue is when I select multiple values it errors.

here is my code:

a!multipleDropdownField(
                    label: "Application",
                    labelPosition: "ABOVE",
                    instructions: "Which application does this issue, request link to?  Select as many as needed. currently only can select one",
                    choiceLabels: {
                      "Tech Demo 1",
                      "GFIM Application",
                      "Service Desk",
                      "Other"
                    },
                    choiceValues: {
                      "Tech Demo 1",
                      "GFIM Application",
                      "Service Desk",
                      "Other"
                    },
                    value: ri!case.application,
                    saveInto: ri!case.application,
                    searchDisplay: "ON",
                    required: false,
                    validations: {}
                  )

this is the error message I get when I select more than one ,

I cannot be the only person who has had this issue, but I could not find anything online about it other than one guy building a custom expression rule.

is that what is necessary?

thanks