diff --git a/packages/saga-extension/src/contracts.ts b/packages/saga-extension/src/contracts.ts
index 7aed28fa..e5065161 100644
--- a/packages/saga-extension/src/contracts.ts
+++ b/packages/saga-extension/src/contracts.ts
@@ -2,7 +2,7 @@ import type { Saga, Task } from 'redux-saga'
 
 declare module '@redux-eggs/core' {
   interface Egg {
-    readonly sagas?: Saga[]
+    sagas?: Saga[]
   }
 }