Unable to make sense of Maxima Expression as result of integration

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Hi,

with sage 7.1 I tried to compute the following integral. I am not sure it has a closed form expression, that is what I wanted to see.

maxima._eval_line(":lisp (ext:set-limit 'ext:heap-size 0)", wait_for_prompt=False)

from sage.symbolic.integration.integral import definite_integral

var('k')

definite_integral(sin(k*x)/x*erf(x^2), x, 0, oo)

What I get is

TypeError: unable to make sense of Maxima expression '\\*z\\*' in Sage

Nothing useful turned up when I googled for it. What does it mean and what is going wrong?

Thank you