diff --git a/src/runtime/server/middleware/session/index.ts b/src/runtime/server/middleware/session/index.ts
index 6ee76e1..fb52243 100644
--- a/src/runtime/server/middleware/session/index.ts
+++ b/src/runtime/server/middleware/session/index.ts
@@ -121,6 +121,20 @@ const getSession = async (event: H3Event): Promise<null | Session> => {
   return session
 }
 
+const getImmutableSession = (session: Session) => {
+  const immutableSession = { ...session }
+  const properties = ['id', 'createdAt', 'ip']
+
+  properties.forEach((property) => {
+    Object.defineProperty(immutableSession, property, {
+      writable: false,
+      configurable: false
+    })
+  })
+
+  return immutableSession as Session
+}
+
 const updateSessionExpirationDate = (session: Session, event: H3Event) => {
   const now = new Date()
   safeSetCookie(event, SESSION_COOKIE_NAME, session.id, now)
@@ -142,7 +156,7 @@ const ensureSession = async (event: H3Event) => {
   }
 
   event.context.sessionId = session.id
-  event.context.session = session
+  event.context.session = getImmutableSession(session)
   return session
 }
 
diff --git a/src/types.ts b/src/types.ts
index af9b8ce..6b68f25 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -183,9 +183,15 @@ export interface ModulePublicRuntimeConfig {
 }
 
 export declare interface Session {
-  id: string;
-  createdAt: Date;
-  ip?: string;
+  readonly id: string;
+  readonly createdAt: Date;
+  readonly ip?: string;
 
   [key: string]: any;
 }
+
+declare module 'h3' {
+  interface H3EventContext {
+    session: Session
+  }
+}