ORA-30484 aliasing analytics column

I'm running an analytical SELECT in 9.2.0.4.0 under 9.2.0.6.0 SQL*Plus:

SELECT first_time, first_time - LAG(first_time) OVER (ORDER BY first_time)=20
FROM v$log_history;

And it works as expected. However, if I try to alias the second column:

SELECT first_time, first_time - LAG(first_time) "SECONDS" OVER (ORDER BY first_time)=20
FROM v$log_history;

It blows up with "ORA-30484: missing window specification for this = function".

Huh? There's gotta be something obvious I'm missing here.

TIA,
Rich

Rich Jesse                        System/Database Administrator
rich.jesse_at_quadtechworld.com      QuadTech, Sussex, WI USA

Disclaimer: Where's my old classmate, Alan?

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