diff --git a/packages/material-ui/src/Tooltip/Tooltip.d.ts b/packages/material-ui/src/Tooltip/Tooltip.d.ts
index 4241b22bb560b8..539c058c5f1414 100644
--- a/packages/material-ui/src/Tooltip/Tooltip.d.ts
+++ b/packages/material-ui/src/Tooltip/Tooltip.d.ts
@@ -41,6 +41,7 @@ export interface TooltipProps
 export type TooltipClassKey =
   | 'popper'
   | 'popperInteractive'
+  | 'popperArrow'
   | 'tooltip'
   | 'tooltipArrow'
   | 'arrow'