diff --git a/packages/react-base16-styling/test/index.test.ts b/packages/react-base16-styling/test/index.test.ts
index e45bf789..5f765a5d 100644
--- a/packages/react-base16-styling/test/index.test.ts
+++ b/packages/react-base16-styling/test/index.test.ts
@@ -127,14 +127,14 @@ test('createStyling (custom)', () => {
     testClass: 'customClass',
     testStyle: { height: 0 },
     testFunc: (styling: Styling, arg: string) => ({
-      className: `${styling.className} customClass--${arg}`,
+      className: `${styling.className!} customClass--${arg}`,
       style: {
         ...styling.style,
         border: 0,
       },
     }),
     testFuncNoStyle: (styling: Styling, arg: string) => ({
-      className: `${styling.className} customClass--${arg}`,
+      className: `${styling.className!} customClass--${arg}`,
       style: {
         ...styling.style,
         border: 0,