diff --git a/frontend_tests/node_tests/popovers.js b/frontend_tests/node_tests/popovers.js
index 13bca5c2ee..9b91769358 100644
--- a/frontend_tests/node_tests/popovers.js
+++ b/frontend_tests/node_tests/popovers.js
@@ -50,6 +50,7 @@ const alice = {
     email: 'alice@example.com',
     full_name: 'Alice Smith',
     user_id: 42,
+    avatar_version: 5,
     is_guest: false,
     is_admin: false,
 };
@@ -184,13 +185,16 @@ run_test('sender_hover', () => {
     });
 
     $('.user_popover_email').each = noop;
-
     const image_stubber = make_image_stubber();
-
+    window.location = {
+        href: 'http://chat.zulip.org/',
+    };
+    const base_url = window.location.href;
     handler.call(target, e);
 
     const avatar_img = image_stubber.get(0);
-    assert.equal(avatar_img.src, 'avatar/42/medium');
+    const expected_url = new URL('avatar/42/medium?v=' + alice.avatar_version, base_url);
+    assert.equal(avatar_img.src.toString(), expected_url.toString());
 
     // todo: load image
 });
diff --git a/static/js/popovers.js b/static/js/popovers.js
index 56f381d4e0..38b14e17ad 100644
--- a/static/js/popovers.js
+++ b/static/js/popovers.js
@@ -94,8 +94,10 @@ function init_email_clipboard() {
 }
 
 function load_medium_avatar(user, elt) {
-    const user_avatar_url = "avatar/" + user.user_id + "/medium";
+    const avatar_path = "avatar/" + user.user_id + "/medium?v=" + user.avatar_version;
+    const user_avatar_url = new URL(avatar_path, window.location.href);
     const sender_avatar_medium = new Image();
+
     sender_avatar_medium.src = user_avatar_url;
     $(sender_avatar_medium).on("load", function () {
         elt.css("background-image", "url(" + $(this).attr("src") + ")");
diff --git a/static/js/user_events.js b/static/js/user_events.js
index eb9a14518a..8c84aef111 100644
--- a/static/js/user_events.js
+++ b/static/js/user_events.js
@@ -69,6 +69,7 @@ exports.update_person = function update(person) {
     if (Object.prototype.hasOwnProperty.call(person, 'avatar_url')) {
         const url = person.avatar_url;
         person_obj.avatar_url = url;
+        person_obj.avatar_version = person.avatar_version;
 
         if (people.is_my_user_id(person.user_id)) {
             page_params.avatar_source = person.avatar_source;
diff --git a/templates/zerver/api/changelog.md b/templates/zerver/api/changelog.md
index 36e2d85a06..c8755c4df1 100644
--- a/templates/zerver/api/changelog.md
+++ b/templates/zerver/api/changelog.md
@@ -10,6 +10,15 @@ below features are supported.
 
 ## Changes in Zulip 2.2
 
+**Feature level 6**
+* [`GET /events`](/api/get-events-from-queue): `realm_user` events to
+  update a user's avatar now include the `avatar_version` field, which
+  is important for correctly refetching medium-size avatar images when
+  the user's avatar changes.
+* [`GET /users`](/api/get-all-users) and [`GET
+  /users/{user_id}`](/api/get-user): User objects now contain the
+  `avatar_version` field as well.
+
 **Feature level 5**
 * [`GET /events`](/api/get-events-from-queue): `realm_bot` events,
   sent when changes are made to bot users, now contain an
diff --git a/version.py b/version.py
index 74b1a2b671..0edc16c0a1 100644
--- a/version.py
+++ b/version.py
@@ -29,7 +29,7 @@ DESKTOP_WARNING_VERSION = "5.2.0"
 #
 # Changes should be accompanied by documentation explaining what the
 # new level means in templates/zerver/api/changelog.md.
-API_FEATURE_LEVEL = 5
+API_FEATURE_LEVEL = 6
 
 # Bump the minor PROVISION_VERSION to indicate that folks should provision
 # only when going from an old version of the code to a newer version. Bump
diff --git a/zerver/lib/actions.py b/zerver/lib/actions.py
index 16a248b403..b9ece499d0 100644
--- a/zerver/lib/actions.py
+++ b/zerver/lib/actions.py
@@ -3263,10 +3263,11 @@ def notify_avatar_url_change(user_profile: UserProfile) -> None:
                    bot_owner_user_ids(user_profile))
 
     payload = dict(
-        email=user_profile.email,
         avatar_source=user_profile.avatar_source,
         avatar_url=avatar_url(user_profile),
         avatar_url_medium=avatar_url(user_profile, medium=True),
+        avatar_version=user_profile.avatar_version,
+        email=user_profile.email,
         user_id=user_profile.id
     )
 
diff --git a/zerver/lib/users.py b/zerver/lib/users.py
index ab63365949..894c6fce96 100644
--- a/zerver/lib/users.py
+++ b/zerver/lib/users.py
@@ -315,6 +315,7 @@ def format_user_row(realm: Realm, acting_user: UserProfile, row: Dict[str, Any],
         email=row['email'],
         user_id=row['id'],
         avatar_url=avatar_url,
+        avatar_version=row['avatar_version'],
         is_admin=is_admin,
         is_guest=is_guest,
         is_bot=is_bot,
diff --git a/zerver/tests/test_custom_profile_data.py b/zerver/tests/test_custom_profile_data.py
index 80facd068e..b8f16322bb 100644
--- a/zerver/tests/test_custom_profile_data.py
+++ b/zerver/tests/test_custom_profile_data.py
@@ -672,14 +672,14 @@ class ListCustomProfileFieldTest(CustomProfileFieldTestCase):
 
         expected_keys_for_iago = {
             "delivery_email",
-            "email", "user_id", "avatar_url", "is_admin", "is_guest", "is_bot",
+            "email", "user_id", "avatar_url", "avatar_version", "is_admin", "is_guest", "is_bot",
             "full_name", "timezone", "is_active", "date_joined", "profile_data"}
         self.assertEqual(set(iago_raw_data.keys()), expected_keys_for_iago)
         self.assertNotEqual(iago_raw_data["profile_data"], {})
 
         expected_keys_for_test_bot = {
             "delivery_email",
-            "email", "user_id", "avatar_url", "is_admin", "is_guest", "is_bot", "full_name",
+            "email", "user_id", "avatar_url", "avatar_version", "is_admin", "is_guest", "is_bot", "full_name",
             "timezone", "is_active", "date_joined", "bot_type", "bot_owner_id"}
         self.assertEqual(set(test_bot_raw_data.keys()), expected_keys_for_test_bot)
         self.assertEqual(test_bot_raw_data["bot_type"], 1)
diff --git a/zerver/tests/test_events.py b/zerver/tests/test_events.py
index d4aab01054..de57989fb7 100644
--- a/zerver/tests/test_events.py
+++ b/zerver/tests/test_events.py
@@ -1247,6 +1247,7 @@ class EventsRegisterTest(ZulipTestCase):
                 ('user_id', check_int),
                 ('email', check_string),
                 ('avatar_url', check_none_or(check_string)),
+                ('avatar_version', check_int),
                 ('full_name', check_string),
                 ('is_admin', check_bool),
                 ('is_bot', check_bool),
@@ -1273,6 +1274,7 @@ class EventsRegisterTest(ZulipTestCase):
                 ('user_id', check_int),
                 ('email', check_string),
                 ('avatar_url', check_none_or(check_string)),
+                ('avatar_version', check_int),
                 ('full_name', check_string),
                 ('is_active', check_bool),
                 ('is_admin', check_bool),
@@ -1534,6 +1536,7 @@ class EventsRegisterTest(ZulipTestCase):
                 ('user_id', check_int),
                 ('avatar_url', check_string),
                 ('avatar_url_medium', check_string),
+                ('avatar_version', check_int),
                 ('avatar_source', check_string),
             ])),
         ])
@@ -1547,11 +1550,12 @@ class EventsRegisterTest(ZulipTestCase):
             ('type', equals('realm_user')),
             ('op', equals('update')),
             ('person', check_dict_only([
-                ('email', check_string),
-                ('user_id', check_int),
+                ('avatar_source', check_string),
                 ('avatar_url', check_none_or(check_string)),
                 ('avatar_url_medium', check_none_or(check_string)),
-                ('avatar_source', check_string),
+                ('avatar_version', check_int),
+                ('email', check_string),
+                ('user_id', check_int),
             ])),
         ])
         events = self.do_test(
@@ -1589,9 +1593,10 @@ class EventsRegisterTest(ZulipTestCase):
             ('person', check_dict_only([
                 ('email', check_string),
                 ('user_id', check_int),
+                ('avatar_source', check_string),
                 ('avatar_url', check_string),
                 ('avatar_url_medium', check_string),
-                ('avatar_source', check_string),
+                ('avatar_version', check_int),
             ])),
         ])
         do_set_realm_property(self.user_profile.realm, "email_address_visibility",
diff --git a/zerver/tests/test_home.py b/zerver/tests/test_home.py
index 8b9de34748..d6228cf28d 100644
--- a/zerver/tests/test_home.py
+++ b/zerver/tests/test_home.py
@@ -604,6 +604,7 @@ class HomeTest(ZulipTestCase):
 
         self.assertEqual(sorted(cross_bots, key=by_email), sorted([
             dict(
+                avatar_version=email_gateway_bot.avatar_version,
                 bot_owner_id=None,
                 bot_type=1,
                 email=email_gateway_bot.email,
@@ -616,6 +617,7 @@ class HomeTest(ZulipTestCase):
                 is_guest=False
             ),
             dict(
+                avatar_version=email_gateway_bot.avatar_version,
                 bot_owner_id=None,
                 bot_type=1,
                 email=notification_bot.email,
@@ -628,6 +630,7 @@ class HomeTest(ZulipTestCase):
                 is_guest=False
             ),
             dict(
+                avatar_version=email_gateway_bot.avatar_version,
                 bot_owner_id=None,
                 bot_type=1,
                 email=welcome_bot.email,