A [wikipedia article](http://en.wikipedia.org/wiki/Lead_dioxide) suggests that lead dioxide is produced by this reaction:
$$\ce{Pb3O4 + 4 HNO3 → PbO2 + 2 Pb(NO3)2 + 2 H2O}$$

The same article also suggests that lead dioxide reacts with nitric acid in the following way:
$$\ce{2 PbO2 + 4 HNO3 → 2 Pb(NO3)2 + 2 H2O + O2}$$

I am unable to understand why then, in the first reaction, $\ce{PbO2}$ doesn't further react with the residual nitric acid. Is it because the quantity of the acid is regulated? Or is there some error in the reactions?