diff --git a/types/slate/index.d.ts b/types/slate/index.d.ts
index 22cf22f8ef..567b7ee52e 100644
--- a/types/slate/index.d.ts
+++ b/types/slate/index.d.ts
@@ -299,7 +299,7 @@ export class Text extends Immutable.Record({}) {
     ): Immutable.Set<Mark>;
     getMarks(): Immutable.OrderedSet<Mark>;
     getMarksAsArray(): Mark[];
-    getMarksAtIndex(index: number): Mark;
+    getMarksAtIndex(index: number): Immutable.OrderedSet<Mark>;
     getNode(key: string): Node | null;
     getPath(key: string | Path): Path;
     hasNode(key: string): boolean;