diff --git a/packages/material-ui/src/Collapse/Collapse.d.ts b/packages/material-ui/src/Collapse/Collapse.d.ts
index cedab407a13ce6..19f6be1e45f17a 100644
--- a/packages/material-ui/src/Collapse/Collapse.d.ts
+++ b/packages/material-ui/src/Collapse/Collapse.d.ts
@@ -11,7 +11,7 @@ export interface CollapseProps extends StandardProps<TransitionProps, CollapseCl
   timeout?: TransitionProps['timeout'] | 'auto';
 }
 
-export type CollapseClassKey = 'container' | 'entered' | 'wrapper' | 'wrapperInner';
+export type CollapseClassKey = 'container' | 'entered' | 'hidden' | 'wrapper' | 'wrapperInner';
 
 declare const Collapse: React.ComponentType<CollapseProps>;