diff --git a/src/course-libraries/CourseLibraries.test.tsx b/src/course-libraries/CourseLibraries.test.tsx
index caa20497cd..c4480a9c36 100644
--- a/src/course-libraries/CourseLibraries.test.tsx
+++ b/src/course-libraries/CourseLibraries.test.tsx
@@ -28,7 +28,7 @@ mockUseLibBlockMetadata.applyMock();
 
 const searchParamsGetMock = jest.fn();
 let axiosMock: MockAdapter;
-let mockShowToast: (message: string, action?: ToastActionData | undefined) => void;
+let mockShowToast: (message: string, action?: ToastActionData) => void;
 let queryClient: QueryClient;
 
 jest.mock('../studio-home/hooks', () => ({
diff --git a/src/course-unit/preview-changes/index.test.tsx b/src/course-unit/preview-changes/index.test.tsx
index 3cae24bd95..0d017ec240 100644
--- a/src/course-unit/preview-changes/index.test.tsx
+++ b/src/course-unit/preview-changes/index.test.tsx
@@ -48,7 +48,7 @@ const render = (eventData?: LibraryChangesMessageData) => {
 };
 
 let axiosMock: MockAdapter;
-let mockShowToast: (message: string, action?: ToastActionData | undefined) => void;
+let mockShowToast: (message: string, action?: ToastActionData) => void;
 
 describe('<IframePreviewLibraryXBlockChanges />', () => {
   beforeEach(() => {
diff --git a/src/library-authoring/add-content/AddContent.test.tsx b/src/library-authoring/add-content/AddContent.test.tsx
index 5b1bb65261..58c06490d3 100644
--- a/src/library-authoring/add-content/AddContent.test.tsx
+++ b/src/library-authoring/add-content/AddContent.test.tsx
@@ -68,7 +68,7 @@ const renderWithContainer = (containerId: string, containerType: 'unit' | 'secti
 };
 
 let axiosMock: MockAdapter;
-let mockShowToast: (message: string, action?: ToastActionData | undefined) => void;
+let mockShowToast: (message: string, action?: ToastActionData) => void;
 
 describe('<AddContent />', () => {
   beforeEach(() => {
diff --git a/src/library-authoring/components/ComponentDeleter.test.tsx b/src/library-authoring/components/ComponentDeleter.test.tsx
index b34a1180b7..4d98547764 100644
--- a/src/library-authoring/components/ComponentDeleter.test.tsx
+++ b/src/library-authoring/components/ComponentDeleter.test.tsx
@@ -35,7 +35,7 @@ const renderArgs = {
   ),
 };
 
-let mockShowToast: { (message: string, action?: ToastActionData | undefined): void; mock?: any; };
+let mockShowToast: { (message: string, action?: ToastActionData): void; mock?: any; };
 
 describe('<ComponentDeleter />', () => {
   beforeEach(() => {
diff --git a/src/library-authoring/containers/ContainerDeleter.test.tsx b/src/library-authoring/containers/ContainerDeleter.test.tsx
index c53b79db1c..829df4f58d 100644
--- a/src/library-authoring/containers/ContainerDeleter.test.tsx
+++ b/src/library-authoring/containers/ContainerDeleter.test.tsx
@@ -51,7 +51,7 @@ const renderArgs = {
   ),
 };
 
-let mockShowToast: { (message: string, action?: ToastActionData | undefined): void; mock?: any; };
+let mockShowToast: { (message: string, action?: ToastActionData): void; mock?: any; };
 
 [
   'unit' as const,
diff --git a/src/library-authoring/containers/ContainerInfo.test.tsx b/src/library-authoring/containers/ContainerInfo.test.tsx
index 703f0326a4..556cd95edf 100644
--- a/src/library-authoring/containers/ContainerInfo.test.tsx
+++ b/src/library-authoring/containers/ContainerInfo.test.tsx
@@ -128,7 +128,7 @@ const render = (
   });
 };
 let axiosMock: MockAdapter;
-let mockShowToast: { (message: string, action?: ToastActionData | undefined): void; mock?: any; };
+let mockShowToast: { (message: string, action?: ToastActionData): void; mock?: any; };
 
 [
   {
diff --git a/src/library-authoring/section-subsections/LibrarySectionSubsectionPage.test.tsx b/src/library-authoring/section-subsections/LibrarySectionSubsectionPage.test.tsx
index da04137738..d95919a6ea 100644
--- a/src/library-authoring/section-subsections/LibrarySectionSubsectionPage.test.tsx
+++ b/src/library-authoring/section-subsections/LibrarySectionSubsectionPage.test.tsx
@@ -34,7 +34,7 @@ const libraryTitle = mockContentLibrary.libraryData.title;
 
 let axiosMock: MockAdapter;
 let queryClient: QueryClient;
-let mockShowToast: (message: string, action?: ToastActionData | undefined) => void;
+let mockShowToast: (message: string, action?: ToastActionData) => void;
 
 mockClipboardEmpty.applyMock();
 mockGetContainerMetadata.applyMock();
diff --git a/src/library-authoring/units/LibraryUnitPage.test.tsx b/src/library-authoring/units/LibraryUnitPage.test.tsx
index 1f9fe10eac..51854b6331 100644
--- a/src/library-authoring/units/LibraryUnitPage.test.tsx
+++ b/src/library-authoring/units/LibraryUnitPage.test.tsx
@@ -33,7 +33,7 @@ const path = '/library/:libraryId/*';
 const libraryTitle = mockContentLibrary.libraryData.title;
 
 let axiosMock: MockAdapter;
-let mockShowToast: (message: string, action?: ToastActionData | undefined) => void;
+let mockShowToast: (message: string, action?: ToastActionData) => void;
 
 mockClipboardEmpty.applyMock();
 mockGetContainerMetadata.applyMock();