diff --git a/packages/netlify-cms-core/src/components/App/App.js b/packages/netlify-cms-core/src/components/App/App.js
index f4d1e9df..645a0916 100644
--- a/packages/netlify-cms-core/src/components/App/App.js
+++ b/packages/netlify-cms-core/src/components/App/App.js
@@ -255,7 +255,7 @@ class App extends React.Component {
 function mapStateToProps(state) {
   const { auth, config, collections, globalUI, mediaLibrary } = state;
   const user = auth.user;
-  const isFetching = globalUI.get('isFetching');
+  const isFetching = globalUI.isFetching;
   const publishMode = config.publish_mode;
   const useMediaLibrary = !mediaLibrary.get('externalLibrary');
   const showMediaButton = mediaLibrary.get('showMediaButton');
diff --git a/packages/netlify-cms-core/src/components/Editor/Editor.js b/packages/netlify-cms-core/src/components/Editor/Editor.js
index 516d8e54..2a2e27ac 100644
--- a/packages/netlify-cms-core/src/components/Editor/Editor.js
+++ b/packages/netlify-cms-core/src/components/Editor/Editor.js
@@ -436,7 +436,7 @@ function mapStateToProps(state, ownProps) {
   const hasChanged = entryDraft.get('hasChanged');
   const displayUrl = config.display_url;
   const hasWorkflow = config.publish_mode === EDITORIAL_WORKFLOW;
-  const useOpenAuthoring = globalUI.get('useOpenAuthoring', false);
+  const useOpenAuthoring = globalUI.useOpenAuthoring;
   const isModification = entryDraft.getIn(['entry', 'isModification']);
   const collectionEntriesLoaded = !!entries.getIn(['pages', collectionName]);
   const unPublishedEntry = selectUnpublishedEntry(state, collectionName, slug);
diff --git a/packages/netlify-cms-core/src/components/Workflow/Workflow.js b/packages/netlify-cms-core/src/components/Workflow/Workflow.js
index cd3dc3e8..6099bad5 100644
--- a/packages/netlify-cms-core/src/components/Workflow/Workflow.js
+++ b/packages/netlify-cms-core/src/components/Workflow/Workflow.js
@@ -138,7 +138,7 @@ class Workflow extends Component {
 function mapStateToProps(state) {
   const { collections, config, globalUI } = state;
   const isEditorialWorkflow = config.publish_mode === EDITORIAL_WORKFLOW;
-  const isOpenAuthoring = globalUI.get('useOpenAuthoring', false);
+  const isOpenAuthoring = globalUI.useOpenAuthoring;
   const returnObj = { collections, isEditorialWorkflow, isOpenAuthoring };
 
   if (isEditorialWorkflow) {
diff --git a/packages/netlify-cms-core/src/reducers/__tests__/globalUI.js b/packages/netlify-cms-core/src/reducers/__tests__/globalUI.js
index d84617a9..6d200821 100644
--- a/packages/netlify-cms-core/src/reducers/__tests__/globalUI.js
+++ b/packages/netlify-cms-core/src/reducers/__tests__/globalUI.js
@@ -1,50 +1,43 @@
-import { Map } from 'immutable';
-import { USE_OPEN_AUTHORING } from 'Actions/auth';
+import { USE_OPEN_AUTHORING } from '../../actions/auth';
 import {
   DEPLOY_PREVIEW_REQUEST,
   DEPLOY_PREVIEW_SUCCESS,
   DEPLOY_PREVIEW_FAILURE,
-} from 'Actions/deploys';
-import { ENTRY_REQUEST, ENTRY_SUCCESS, ENTRY_FAILURE } from 'Actions/entries';
+} from '../../actions/deploys';
+import { ENTRY_REQUEST, ENTRY_SUCCESS, ENTRY_FAILURE } from '../../actions/entries';
 import reducer from '../globalUI';
 
 describe('globalUI', () => {
   it('should set isFetching to true on entry request', () => {
-    expect(reducer(Map({ isFetching: false }), { type: ENTRY_REQUEST })).toEqual(
-      Map({ isFetching: true }),
-    );
+    expect(reducer({ isFetching: false }, { type: ENTRY_REQUEST })).toEqual({ isFetching: true });
   });
 
   it('should set isFetching to false on entry success', () => {
-    expect(reducer(Map({ isFetching: true }), { type: ENTRY_SUCCESS })).toEqual(
-      Map({ isFetching: false }),
-    );
+    expect(reducer({ isFetching: true }, { type: ENTRY_SUCCESS })).toEqual({ isFetching: false });
   });
 
   it('should set isFetching to false on entry failure', () => {
-    expect(reducer(Map({ isFetching: true }), { type: ENTRY_FAILURE })).toEqual(
-      Map({ isFetching: false }),
-    );
+    expect(reducer({ isFetching: true }, { type: ENTRY_FAILURE })).toEqual({ isFetching: false });
   });
 
   it('should not change state on deploy preview request', () => {
-    const state = Map({ isFetching: false });
+    const state = { isFetching: false };
     expect(reducer(state, { type: DEPLOY_PREVIEW_REQUEST })).toBe(state);
   });
 
   it('should not change state on deploy preview success', () => {
-    const state = Map({ isFetching: true });
+    const state = { isFetching: true };
     expect(reducer(state, { type: DEPLOY_PREVIEW_SUCCESS })).toBe(state);
   });
 
   it('should not change state on deploy preview failure', () => {
-    const state = Map({ isFetching: true });
+    const state = { isFetching: true };
     expect(reducer(state, { type: DEPLOY_PREVIEW_FAILURE })).toBe(state);
   });
 
   it('should set useOpenAuthoring to true on USE_OPEN_AUTHORING', () => {
-    expect(reducer(Map({ useOpenAuthoring: false }), { type: USE_OPEN_AUTHORING })).toEqual(
-      Map({ useOpenAuthoring: true }),
-    );
+    expect(reducer({ useOpenAuthoring: false }, { type: USE_OPEN_AUTHORING })).toEqual({
+      useOpenAuthoring: true,
+    });
   });
 });
diff --git a/packages/netlify-cms-core/src/reducers/globalUI.js b/packages/netlify-cms-core/src/reducers/globalUI.ts
similarity index 53%
rename from packages/netlify-cms-core/src/reducers/globalUI.js
rename to packages/netlify-cms-core/src/reducers/globalUI.ts
index 5f2e0862..6c5876a4 100644
--- a/packages/netlify-cms-core/src/reducers/globalUI.js
+++ b/packages/netlify-cms-core/src/reducers/globalUI.ts
@@ -1,5 +1,11 @@
-import { Map } from 'immutable';
-import { USE_OPEN_AUTHORING } from 'Actions/auth';
+import { AnyAction } from 'redux';
+import { produce } from 'immer';
+import { USE_OPEN_AUTHORING } from '../actions/auth';
+
+export type GlobalUI = {
+  isFetching: boolean;
+  useOpenAuthoring: boolean;
+};
 
 const LOADING_IGNORE_LIST = [
   'DEPLOY_PREVIEW',
@@ -8,26 +14,30 @@ const LOADING_IGNORE_LIST = [
   'STATUS_FAILURE',
 ];
 
-function ignoreWhenLoading(action) {
+function ignoreWhenLoading(action: AnyAction) {
   return LOADING_IGNORE_LIST.some(type => action.type.includes(type));
 }
 
+const defaultState: GlobalUI = {
+  isFetching: false,
+  useOpenAuthoring: false,
+};
+
 /**
  * Reducer for some global UI state that we want to share between components
  */
-function globalUI(state = Map({ isFetching: false, useOpenAuthoring: false }), action) {
+const globalUI = produce((state: GlobalUI, action: AnyAction) => {
   // Generic, global loading indicator
   if (!ignoreWhenLoading(action) && action.type.includes('REQUEST')) {
-    return state.set('isFetching', true);
+    state.isFetching = true;
   } else if (
     !ignoreWhenLoading(action) &&
     (action.type.includes('SUCCESS') || action.type.includes('FAILURE'))
   ) {
-    return state.set('isFetching', false);
+    state.isFetching = false;
   } else if (action.type === USE_OPEN_AUTHORING) {
-    return state.set('useOpenAuthoring', true);
+    state.useOpenAuthoring = true;
   }
-  return state;
-}
+}, defaultState);
 
 export default globalUI;
diff --git a/packages/netlify-cms-core/src/types/redux.ts b/packages/netlify-cms-core/src/types/redux.ts
index d1ac97fc..6afba7b1 100644
--- a/packages/netlify-cms-core/src/types/redux.ts
+++ b/packages/netlify-cms-core/src/types/redux.ts
@@ -8,6 +8,7 @@ import { Status } from '../reducers/status';
 import { Medias } from '../reducers/medias';
 import { Deploys } from '../reducers/deploys';
 import { Search } from '../reducers/search';
+import { GlobalUI } from '../reducers/globalUI';
 
 export type CmsBackendType =
   | 'azure'
@@ -684,6 +685,7 @@ export interface State {
   cursors: Cursors;
   collections: Collections;
   deploys: Deploys;
+  globalUI: GlobalUI;
   editorialWorkflow: EditorialWorkflow;
   entries: Entries;
   entryDraft: EntryDraft;