diff --git a/types/chart.js/index.d.ts b/types/chart.js/index.d.ts
index 111c8da57f..6becfaba40 100644
--- a/types/chart.js/index.d.ts
+++ b/types/chart.js/index.d.ts
@@ -14,6 +14,7 @@
 //                 Alexandros Dorodoulis <https://github.com/alexdor>
 //                 Manuel Heidrich <https://github.com/mahnuh>
 //                 Conrad Holtzhausen <https://github.com/Conrad777>
+//                 Adrián Caballero <https://github.com/adripanico>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.3
 
@@ -146,8 +147,8 @@ declare namespace Chart {
     }
 
     interface ChartTooltipItem {
-        xLabel?: string;
-        yLabel?: string;
+        xLabel?: string | number;
+        yLabel?: string | number;
         datasetIndex?: number;
         index?: number;
     }