diff --git a/types/c3/index.d.ts b/types/c3/index.d.ts
index d68027f7d5..28f301237c 100644
--- a/types/c3/index.d.ts
+++ b/types/c3/index.d.ts
@@ -880,6 +880,7 @@ export interface ChartAPI {
         keys?: { x?: string; value: string[]; }
         rows?: PrimitiveArray[];
         columns?: PrimitiveArray[];
+        xs?: { [key: string]: string };
         names?: { [key: string]: string };
         classes?: { [key: string]: string };
         categories?: string[];