Simple IF function with blank option

Hello,
I'm trying to create a simple IF function in which:
I compare cell A1 to a known value in cell B1, if their text is the same then I get true value of "OK" and if they are not then I get a false value of "ERROR". (eg if B1 has value of "5" and I type in A1 "5" I get OK, and if I type in A1 "3" I get ERROR), Here is the function:
=IF(A1=B1, "OK", "ERROR")
Now the problem is that before I type something in cell A it already shows ERR0R because A is blank and B is not and they are not equal. I want the same function but when A is empty it will not show ERROR but just remain blank.

Thank you

=if(A1<>"",IF(A1=B1, "OK", "ERROR"),"")
Try above formula