diff problem



I have Maxima 5.9.0 compiled under slackware linux with CLISP. Unfortunately, 
I'm having some problems. When I put the expression "diff(x^2,x);", it returns 
only (d/dy)(x^2), as if i had put the apostrophe before the expression.
Under windows, it returns the result (2 x).
Any sugegstions?

Thanks

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Pedro Ferreira