diff --git a/package.json b/package.json
index f9f0675c..9de8e8e3 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@artemisag/mobx-async-store",
-  "version": "7.1.0",
+  "version": "7.1.1",
   "license": "MIT",
   "module": "dist/mobx-async-store.esm.js",
   "main": "dist/mobx-async-store.cjs.js",
diff --git a/spec/Model.spec.ts b/spec/Model.spec.ts
index 668f6f93..fcc4995d 100644
--- a/spec/Model.spec.ts
+++ b/spec/Model.spec.ts
@@ -943,8 +943,15 @@ describe('Model', () => {
         description: 'Example description'
       })
 
+      const note2 = store.add('notes', {
+        id: '11',
+        description: 'Example description'
+      })
+
       todo.notes.add(note)
       note.description = 'something different'
+      todo.notes.replace([note, note2])
+
       expect(todo.dirtyAttributes).toEqual(blankSet)
       expect(note.dirtyAttributes.size).toEqual(1)
       expect(note.dirtyAttributes).toContain('description')
diff --git a/spec/Store.spec.ts b/spec/Store.spec.ts
index 0bbb25c7..62a3e538 100644
--- a/spec/Store.spec.ts
+++ b/spec/Store.spec.ts
@@ -275,10 +275,6 @@ describe('Store', () => {
     })
   })
 
-  it('has observable data property', () => {
-    expect(isObservable(store.data)).toBe(true)
-  })
-
   it('sets network configuration properties', () => {
     expect(store.baseUrl).toEqual(mockBaseUrl)
     expect(store.defaultFetchOptions).toEqual(mockFetchOptions)
@@ -300,11 +296,11 @@ describe('Store', () => {
 
   it('initializes data observable', () => {
     const map = new Map()
-    expect(toJS(store.data)).toEqual({
-      todos: { cache: map, meta: map, records: map },
-      notes: { cache: map, meta: map, records: map },
-      categories: { cache: map, meta: map, records: map },
-      tags: { cache: map, meta: map, records: map }
+    expect(store.data).toEqual({
+      todos: { cache: new Map(), meta: new Map(), records: new Map() },
+      notes: { cache: new Map(), meta: new Map(), records: new Map() },
+      categories: { cache: new Map(), meta: new Map(), records: new Map() },
+      tags: { cache: new Map(), meta: new Map(), records: new Map() }
     })
   })
 
diff --git a/src/Model.ts b/src/Model.ts
index 8b6d9946..3e8d0268 100644
--- a/src/Model.ts
+++ b/src/Model.ts
@@ -231,7 +231,7 @@ class Model {
 
     return Object.keys(this.attributes).reduce((dirtyAccumulator, attr) => {
       const currentValue = this.attributes[attr]
-      const previousValue = this.previousSnapshot.attributes[attr]
+      const previousValue = this.persistedOrFirstSnapshot.attributes[attr]
 
       if (isObject(currentValue)) {
         const currentToPreviousDiff = diff(currentValue, previousValue)
diff --git a/src/Store.ts b/src/Store.ts
index d3d48d0f..2d257c8e 100644
--- a/src/Store.ts
+++ b/src/Store.ts
@@ -15,7 +15,6 @@ import cloneDeep from 'lodash/cloneDeep'
  */
 
 const mobxAnnotations = {
-  data: observable,
   lastResponseHeaders: observable,
   loadingStates: observable,
   loadedStates: observable,
@@ -69,9 +68,9 @@ class Store {
    * Stores data by type.
    * {
    *   todos: {
-   *     records: observable.map(), // records by id
-   *     cache: observable.map(), // cached ids by url
-   *     meta: observable.map() // meta information by url
+   *     records: new Map(), // records by id
+   *     cache: new Map(), // cached ids by url
+   *     meta: new Map() // meta information by url
    *   }
    * }
    *
@@ -680,9 +679,9 @@ class Store {
     const types = type ? [type] : this.models.map(({ type }) => type)
     types.forEach((type) => {
       this.data[type] = {
-        records: observable.map(),
-        cache: observable.map(),
-        meta: observable.map()
+        records: new Map(),
+        cache: new Map(),
+        meta: new Map()
       }
     })
   }