diff --git a/packages/mui-base/src/FocusTrap/FocusTrap.types.ts b/packages/mui-base/src/FocusTrap/FocusTrap.types.ts
index 462100ec696479..be9cf5ee1e93c3 100644
--- a/packages/mui-base/src/FocusTrap/FocusTrap.types.ts
+++ b/packages/mui-base/src/FocusTrap/FocusTrap.types.ts
@@ -10,7 +10,7 @@ export interface FocusTrapProps {
    * For instance, you can provide the "tabbable" npm dependency.
    * @param {HTMLElement} root
    */
-  getTabbable?: (root: HTMLElement) => ReadonlyArray<HTMLElement>;
+  getTabbable?: (root: HTMLElement) => ReadonlyArray<string>;
   /**
    * This prop extends the `open` prop.
    * It allows to toggle the open state without having to wait for a rerender when changing the `open` prop.
diff --git a/packages/mui-material/src/Unstable_TrapFocus/FocusTrap.tsx b/packages/mui-material/src/Unstable_TrapFocus/FocusTrap.tsx
index 264403eb00eac9..7a404740af6b68 100644
--- a/packages/mui-material/src/Unstable_TrapFocus/FocusTrap.tsx
+++ b/packages/mui-material/src/Unstable_TrapFocus/FocusTrap.tsx
@@ -270,7 +270,7 @@ function FocusTrap(props: FocusTrapProps): React.JSX.Element {
         return;
       }
 
-      let tabbable: ReadonlyArray<string> | HTMLElement[] = [];
+      let tabbable: ReadonlyArray<HTMLElement> = [];
       if (
         doc.activeElement === sentinelStart.current ||
         doc.activeElement === sentinelEnd.current
diff --git a/packages/mui-material/src/Unstable_TrapFocus/FocusTrap.types.ts b/packages/mui-material/src/Unstable_TrapFocus/FocusTrap.types.ts
index be9cf5ee1e93c3..462100ec696479 100644
--- a/packages/mui-material/src/Unstable_TrapFocus/FocusTrap.types.ts
+++ b/packages/mui-material/src/Unstable_TrapFocus/FocusTrap.types.ts
@@ -10,7 +10,7 @@ export interface FocusTrapProps {
    * For instance, you can provide the "tabbable" npm dependency.
    * @param {HTMLElement} root
    */
-  getTabbable?: (root: HTMLElement) => ReadonlyArray<string>;
+  getTabbable?: (root: HTMLElement) => ReadonlyArray<HTMLElement>;
   /**
    * This prop extends the `open` prop.
    * It allows to toggle the open state without having to wait for a rerender when changing the `open` prop.