Required fields not being validated before 'submit a form' action is taken

Created a fill-in pdf form using Adobe Acrobat with several required fields and then a submit button using the 'submit a form' action.   The pdf form will submit even though a required input field hasn't been completed.  It works just fine and gives an error message when all required fields aren't completed, but as soon as one required field is completed (but other required field are not completed), it submits the form.   I don't want them to be able to submit unless all required fields are complete.