C51 8.02/8.05 compiler bug - function parameter overwritten

Hey guys from KEIL, sorry but I have to report this.
Here is a simple code that shows the bug:

typedef unsigned char byte;
byte code zzz[4];
void fff(byte,byte);
void keil_bug(byte flag) {
byte ep = 1;
fff(ep, flag ? 0 : zzz[ep]);
}

and here is compiler output

; FUNCTION _keil_bug (BEGIN)
; SOURCE LINE # 4
;---- Variable 'flag' assigned to Register 'R6' ----
MOV R6,AR7
; SOURCE LINE # 5
;---- Variable 'ep' assigned to Register 'R7' ----
MOV R7,#01H
; SOURCE LINE # 6
MOV A,R6
xJZ ?C0001
MOV R5,#00H
xJMP ?C0002
?C0001:
MOV A,R7
MOV DPTR,#zzz
MOVC A,@A+DPTR
MOV R7,A
MOV R5,A
?C0002:
CALL _fff
; SOURCE LINE # 7
RET
; FUNCTION _keil_bug (END)

first parameter [ep] to function fff() which has to be passed via R7 overwritten by fetched zzz[ep] two instructions before the call :(

This happens on optimization level 7. On level 6 fetched value is moved to R6 which is at least harmless.

I checked evaluation version 8.05 (I'm using 8.02) but it has the same problem.