In the reaction

$$\ce{2 O3 -> 3 O2}$$

the order of reaction that I have been taught is

$$\ce{O\_3 \underset{$k\_{-1}$}{\overset{$k\_{1}$}{<=>}} O\_2 + O}$$
$$\ce{O\_3 + O \overset{$k\_{2}$}{->} 2O\_2}$$

$$\mathrm{rate} = k\_{2}[\ce{O3}][\ce{O}]$$

$$ k\_{1}[\ce{O3}]= k\_{-1}[\ce{O2}][\ce{O}]$$

So $$\mathrm{rate} = \frac{k\_{1}k\_{2}}{k\_{-1}} [\ce{O3}]^2[\ce{O2}]^{-1}$$

What does this $[\ce{O2}]^{-1}$ part mean? For example, initially when there is no $\ce{O2}$, the rate should be $\infty$; how is that possible? Or is it normal and I should accept it?