SPFILE and rollback_segments parameter

I'm stuck and could really use some help. I'm trying to get my rollback segments online on startup by using the initialization parameter "rollback_segments". Previously when I used traditional init.ora file it worked perfectly, but now with the spfile, no such luck. I did "alter system set rollback_segments='(rbs01, rbs02, rbs03, rbs04)' scope=spfile;". Then I did shutdown, startup and got ORA-01092. It works if I specify only one rollback segment, like "alter system set rollback_segments='rbs04' scope=spfile;", but I need them all. I have tried different syntaxes, used lower and upper case, but found no solution.

I can get all the segments online manually after startup.

(Oracle version 9.0.1, Solaris Sparc)

Thanks...

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JKe