diff --git a/extensions/vscode-api-tests/src/singlefolder-tests/state.test.ts b/extensions/vscode-api-tests/src/singlefolder-tests/state.test.ts
index f10edc51b3b..cbe58948d86 100644
--- a/extensions/vscode-api-tests/src/singlefolder-tests/state.test.ts
+++ b/extensions/vscode-api-tests/src/singlefolder-tests/state.test.ts
@@ -5,7 +5,7 @@
 
 import * as assert from 'assert';
 import 'mocha';
-import { ExtensionContext, extensions } from 'vscode';
+import { ExtensionContext, extensions, Uri } from 'vscode';
 
 suite('vscode API - globalState / workspaceState', () => {
 
@@ -16,7 +16,7 @@ suite('vscode API - globalState / workspaceState', () => {
 		extensionContext = (global as any).testExtensionContext;
 	});
 
-	test('state', async () => {
+	test('state basics', async () => {
 		for (const state of [extensionContext.globalState, extensionContext.workspaceState]) {
 			let keys = state.keys();
 			assert.strictEqual(keys.length, 0);
@@ -42,4 +42,39 @@ suite('vscode API - globalState / workspaceState', () => {
 			assert.strictEqual(res, 'default');
 		}
 	});
+
+	test('state - handling of objects', async () => {
+		for (const state of [extensionContext.globalState, extensionContext.workspaceState]) {
+			const keys = state.keys();
+			assert.strictEqual(keys.length, 0);
+
+			state.update('state.test.date', new Date());
+			const date = state.get('state.test.date');
+			assert.ok(typeof date === 'string');
+
+			state.update('state.test.regex', /foo/);
+			const regex = state.get('state.test.regex');
+			assert.ok(typeof regex === 'object' && !(regex instanceof RegExp));
+
+			class Foo { }
+			state.update('state.test.class', new Foo());
+			const clazz = state.get('state.test.class');
+			assert.ok(typeof clazz === 'object' && !(clazz instanceof Foo));
+
+			const cycle: any = { self: null };
+			cycle.self = cycle;
+			assert.throws(() => state.update('state.test.cycle', cycle));
+
+			const uriIn = Uri.parse('/foo/bar');
+			state.update('state.test.uri', uriIn);
+			const uriOut = state.get('state.test.uri') as Uri;
+			assert.ok(uriIn.toString() === Uri.from(uriOut).toString());
+
+			state.update('state.test.null', null);
+			assert.strictEqual(state.get('state.test.null'), null);
+
+			state.update('state.test.undefined', undefined);
+			assert.strictEqual(state.get('state.test.undefined'), undefined);
+		}
+	});
 });
diff --git a/src/vs/workbench/api/common/extHostMemento.ts b/src/vs/workbench/api/common/extHostMemento.ts
index e1dc4f27947..baad57cfd67 100644
--- a/src/vs/workbench/api/common/extHostMemento.ts
+++ b/src/vs/workbench/api/common/extHostMemento.ts
@@ -76,7 +76,15 @@ export class ExtensionMemento implements vscode.Memento {
 	}
 
 	update(key: string, value: any): Promise<void> {
-		this._value![key] = value;
+		if (value !== null && typeof value === 'object') {
+			// Prevent the value from being as-is for until we have
+			// received the change event from the main side by emulating
+			// the treatment of values via JSON parsing and stringifying.
+			// (https://github.com/microsoft/vscode/issues/209479)
+			this._value![key] = JSON.parse(JSON.stringify(value));
+		} else {
+			this._value![key] = value;
+		}
 
 		const record = this._deferredPromises.get(key);
 		if (record !== undefined) {