ListGrid float type validation with negative number

I have a field in DataSource type float:

<field name="WEIGHT" type="float" cellAlign="right" align="left" ></field>

This field is allowed to enter negative number.

Whenever I type "-" a negative symbol, the symbol cannot be displayed in the editor and error message "Must be a valid decimal."

I wonder how to solve this problem

Attached Images

validate.jpg (30.4 KB)