Lemma 89.10.2. Let $\mathcal{F}$ be a category cofibered in groupoids over $\mathcal C_\Lambda$. Then $\mathcal{F}$ satisfies (S1) if the condition of (S1) is assumed to hold only when $A_2 \to A$ is a small extension.

Proof. Proof omitted. Hints: apply Lemma 89.3.3 and use induction similar to the proof of Lemma 89.8.2. $\square$

In your comment you can use Markdown and LaTeX style mathematics (enclose it like $\pi$). A preview option is available if you wish to see how it works out (just click on the eye in the toolbar).