The description of the function FcConfigSetCurrent states: "Sets the current default configuration to config". But after changing the font configuration, the function FcConfigSetCurrent doesn't make it as default configuration. The detailed bug description can be found at: http://linuxtesting.org/results/report?num=S0600
I'm surprised it didn't just crash -- setting the config to the current value would have triggered a bug in the library. This should be fixed now (and do nothing). Your test is not checking the right thing; you should construct a new configuration (using FcConfigCreate or FcInitLoadConfig). fc141b492bab23d58d248fc3b6d34bcb9c5faa99
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