diff --git a/src/runtime/reactivity.ts b/src/runtime/reactivity.ts
index 210e38ec..43ae74b9 100644
--- a/src/runtime/reactivity.ts
+++ b/src/runtime/reactivity.ts
@@ -368,7 +368,7 @@ function delegateAndNotify(
     if (hadKey !== hasKey) {
       notifyReactives(target, KEYCHANGES);
     }
-    if (originalValue !== value) {
+    if (originalValue !== target[getterName](key)) {
       notifyReactives(target, key);
     }
     return ret;
diff --git a/tests/reactivity.test.ts b/tests/reactivity.test.ts
index 9d67f1d5..ed6ef775 100644
--- a/tests/reactivity.test.ts
+++ b/tests/reactivity.test.ts
@@ -1292,6 +1292,12 @@ describe("Collections", () => {
 
       state.add(3); // setting unobserved key doesn't notify
       expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.has(3)).toBe(true); // subscribe to 3
+      state.add(3); // adding observed key doesn't notify if key was already present
+      expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.has(4)).toBe(false); // subscribe to 4
+      state.delete(4); // deleting observed key doesn't notify if key was already not present
+      expect(observer).toHaveBeenCalledTimes(3);
     });
 
     test("iterating on keys returns reactives", async () => {
@@ -1485,6 +1491,12 @@ describe("Collections", () => {
 
       state.set(3, 4); // setting unobserved key doesn't notify
       expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.has(3)).toBe(true); // subscribe to 3
+      state.set(3, 4); // setting the same value doesn't notify
+      expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.has(4)).toBe(false); // subscribe to 4
+      state.delete(4); // deleting observed key doesn't notify if key was already not present
+      expect(observer).toHaveBeenCalledTimes(3);
     });
 
     test("checking for a key with 'get' subscribes the callback to changes to that key", () => {
@@ -1510,6 +1522,12 @@ describe("Collections", () => {
 
       state.set(3, 4); // setting unobserved key doesn't notify
       expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.get(3)).toBe(4); // subscribe to 3
+      state.set(3, 4); // setting the same value doesn't notify
+      expect(observer).toHaveBeenCalledTimes(3);
+      expect(state.get(4)).toBe(undefined); // subscribe to 4
+      state.delete(4); // deleting observed key doesn't notify if key was already not present
+      expect(observer).toHaveBeenCalledTimes(3);
     });
 
     test("getting values returns a reactive", async () => {