diff --git a/test/unit/config/matchers/to-be-positioned-popover.js b/test/unit/config/matchers/to-be-positioned-popover.js
index bb28edce85b76..f646ff291d213 100644
--- a/test/unit/config/matchers/to-be-positioned-popover.js
+++ b/test/unit/config/matchers/to-be-positioned-popover.js
@@ -8,7 +8,7 @@ function toBePositionedPopover( element ) {
 	const pass = element.style.top !== '' && element.style.left !== '';
 	return {
 		pass,
-		message: `Received element is ${ pass ? '' : 'not ' } positioned`,
+		message: () => `Received element is ${ pass ? '' : 'not ' }positioned`,
 	};
 }