Can porque trigger the subjunctive?

This is taken from Tus huellas son mis pasos, a B2 reader I found on Amazon.

My cursory search of the internet suggests that no, it should not, and that the highlighted fragment should use the indicative.

The first part of the highlighted fragment is

Afirma Celia ante la sorpresa de Gozalo porque ella supiera…

If we aren't paying too much attention, it seems reasonable for the second clause to require the subjunctive: the first clause discusses an emotion caused by the second clause. However, the connector is "porque", not "que" or "de que."

Is there something that I am missing?

submitted by /u/naridimh
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