Error when solve sparse symmetric system on 3.6.1 octave

[Giorgos Kourakos]

Hi I've recently updated my octave from 3.2.4 to 3.6.1.
In my program I'm solving a linear system of the form X=A\B where A is symmetric and positive defined but large and sparse(~500000 rows)
In 3.2.4 I was able to solve the system using the above command. In 3.6.1 however I'm getting an error that UMFPACK is not installed. I don't understand why octave tries to solve this with UMFPACK, which is for unsymmetric systems.
Is there anything I can do to solve this without installing the UMFPACK (I'm not admin on the system). Note also that I could solve in 3.6.1 the following system
rand(1000)\rand(1000,1) which is definitelly unsymmetric

Thank you

Giorgos