R help - Feb 2011 - why no "probabilities" from svm.predict?

> library(ROCR)
> library(e1071)
svmres.prob <- svm(traindx, traindy, probability=TRUE)
svmpred.prob <- predict(svmres.prob, testdx, probability = TRUE,
decision.values = TRUE, type="prob")
> print(length(attr(svmpred.prob, "probabilities")))
[1] 0
> print(attr(svmpred.prob, "probabilities"))
NULL
> print(attributes(svmpred.prob)$decision.values)
              /
1   -0.54976883
2   -0.19255459
3   -0.05190025

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