# Kerodon

$\Newextarrow{\xRightarrow}{5,5}{0x21D2}$ $\newcommand\empty{}$

Corollary 4.5.2.21. Suppose we are given a pullback diagram of $\infty$-categories

4.27
$$\begin{gathered}\label{equation:categorical-pullback-square44} \xymatrix@R =50pt@C=50pt{ \operatorname{\mathcal{C}}' \ar [r] \ar [d] & \operatorname{\mathcal{C}}\ar [d]^{U} \\ \operatorname{\mathcal{D}}' \ar [r] & \operatorname{\mathcal{D}}. } \end{gathered}$$

If $U$ is an isofibration, then (4.27) is a categorical pullback square.