diff --git a/packages/test-utils/src/find-vnodes.js b/packages/test-utils/src/find-vnodes.js
index 8579fdd61..58da14867 100644
--- a/packages/test-utils/src/find-vnodes.js
+++ b/packages/test-utils/src/find-vnodes.js
@@ -55,7 +55,7 @@ function findVNodesBySelector (vNode: VNode, selector: string): Array<VNode> {
 
 export default function findVnodes (
   vnode: VNode,
-  vm: Component | null,
+  vm: Component | void,
   selectorType: ?string,
   selector: Object | string
 ): Array<VNode> {
diff --git a/packages/test-utils/src/find.js b/packages/test-utils/src/find.js
index ef983d7f1..1217343d4 100644
--- a/packages/test-utils/src/find.js
+++ b/packages/test-utils/src/find.js
@@ -9,7 +9,7 @@ import getSelectorTypeOrThrow from './get-selector-type'
 import { throwError } from 'shared/util'
 
 export default function find (
-  vm: Component | null,
+  vm: Component | void,
   vnode: VNode | null,
   element: Element,
   selector: Selector
diff --git a/packages/test-utils/src/wrapper.js b/packages/test-utils/src/wrapper.js
index 737bd21d5..882c70121 100644
--- a/packages/test-utils/src/wrapper.js
+++ b/packages/test-utils/src/wrapper.js
@@ -24,7 +24,7 @@ import { orderWatchers } from './order-watchers'
 
 export default class Wrapper implements BaseWrapper {
   +vnode: VNode | null;
-  +vm: Component | null;
+  +vm: Component | void;
   _emitted: { [name: string]: Array<Array<any>> };
   _emittedByOrder: Array<{ name: string, args: Array<any> }>;
   isVm: boolean;