diff --git a/types/c3/index.d.ts b/types/c3/index.d.ts
index 9a006b27aa..79445ee732 100644
--- a/types/c3/index.d.ts
+++ b/types/c3/index.d.ts
@@ -10,8 +10,7 @@ export = c3;
 export as namespace c3;
 
 declare namespace c3 {
-
-    type PrimitiveArray = Array<string | boolean | number>;
+    type PrimitiveArray = Array<string | boolean | number | null>;
     type FormatFunction = (v: any, id: string, i: number, j: number) => void;
 
     interface TargetIds {