diff --git a/src/types.ts b/src/types.ts
index bc3de0a..560d15e 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,7 +1,7 @@
 export const AppModeValues = ["development", "production", "test"] as const;
 export type AppMode = typeof AppModeValues[number];
 export const isAppMode = (value: unknown): value is AppMode => {
-  return value === "development" || value === "production" || value === "test";
+  return AppModeValues.includes(value as AppMode);
 };
 
 export type AppConfig = {