Numberfield Problems with decimalSeparator

Hi everybody, i'm trying to write decimals number like this: 0.96 or 1.00, etc,( 2 decimals), but numberfield does not let me write a decimal with a dot character, but the numberfield let me writes comma instead dot character,

Example i need: 1.90

numberfield let me always: 1,90

this is my code:

Code:

                                     xtype: 'numberfield',                                
                                    defaultType: 'numberfield',
                                    width: 210,
                                    fieldLabel: 'Tax',
                                    labelWidth: 120,
                                    name: 'tax',
                                    hideTrigger: true,
                                   decimalPresicion:2,
                                    allowDecimals:true,
                                  decimalSeparator:'.'

I was testing the examples but all seems clear, do i missing something special?

Thanks.

Extjs: 4.2.1

SenchaArchitect :3,

3.0.3.1382