git pull SSL Certificate Problem

When trying to git pull pkgsrc repo from GitHub I saw an SSL error:

user@host:~/opt/pkgsrc$ git pull
fatal: unable to access '': SSL certificate problem: unable to get local issuer certificate
I tested this guide on Ubuntu 14.04 with Nix package manager.

Note: I was using a git version pulled in from Nix. The git from Ubuntu was working just fine.

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