diff --git a/packages/theme/api-report.md b/packages/theme/api-report.md
index 30dcb7b040..2dc6ab7b55 100644
--- a/packages/theme/api-report.md
+++ b/packages/theme/api-report.md
@@ -64,7 +64,7 @@ export type BackstagePaletteAdditions = {
     error: string;
     text: string;
     link: string;
-    warning: string;
+    warning?: string;
   };
 };