diff --git a/src/types/index.d.ts b/src/types/index.d.ts
index 6e661188a0b..84cf089cad2 100644
--- a/src/types/index.d.ts
+++ b/src/types/index.d.ts
@@ -177,7 +177,7 @@ export interface BubbleDataPoint extends Point {
   /**
    * Bubble radius in pixels (not scaled).
    */
-  r: number;
+  r?: number;
 }
 
 export type BubbleController = DatasetController