How to reformat in-line citations when \nameyeardelim is undefined?

As per the second part of this question, I want to remove the comma from the end of the authors in my in-line citations, e.g., Doe et al., 2013 -> Doe et al. 2013. The solution is to redefine \nameyeardelim:

However, this causes

! LaTeX Error: \nameyeardelim undefined.

I'm using natbib with the default options. How can I overcome this error to remove the comma between the last author and year in my in-line citations?

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You should be able to use \setcitestyle{aysep={}}. – Adam Liter Aug 27 '13 at 20:43
Thank you @Adam, that solved it! – drs Aug 27 '13 at 23:01