Problem in setting up Input Type in Single line field in zoho form

Problem in setting up Input Type in Single line field in zoho form

I have identified a problem while adding a single line field in zoho form, in zoho form we have to add a field name account holder name , now to validate this we want a account holder name in single line for example "Ashish Bhatnagar"

So for this i have selected the input type as Letters Only , but if i select letter only in input type then our customer are not able to add a space between their first name and last name , they have to add their full name without any spaces which is actually not right format , there must be some input type for "Letter and Spaces"