diff --git a/frontend_tests/node_tests/people.js b/frontend_tests/node_tests/people.js
index 8d342a1692..656951e8d9 100644
--- a/frontend_tests/node_tests/people.js
+++ b/frontend_tests/node_tests/people.js
@@ -747,6 +747,12 @@ test_people("message_methods", () => {
         people.small_avatar_url_for_person(maria),
         "https://secure.gravatar.com/avatar/6dbdd7946b58d8b11351fcb27e5cdd55?d=identicon&s=50",
     );
+    assert.equal(
+        people.medium_avatar_url_for_person(maria),
+        "https://secure.gravatar.com/avatar/6dbdd7946b58d8b11351fcb27e5cdd55?d=identicon&s=500",
+    );
+    assert.equal(people.medium_avatar_url_for_person(charles), "/avatar/301/medium");
+    assert.equal(people.medium_avatar_url_for_person(ashton), "/avatar/303/medium");
 
     muted_users.add_muted_user(30);
     assert.deepEqual(people.sender_info_for_recent_topics_row([30]), [
diff --git a/frontend_tests/node_tests/popovers.js b/frontend_tests/node_tests/popovers.js
index 122ec484b4..6b6106111d 100644
--- a/frontend_tests/node_tests/popovers.js
+++ b/frontend_tests/node_tests/popovers.js
@@ -206,12 +206,10 @@ test_ui("sender_hover", ({override, mock_template}) => {
 
     $.create(".user_popover_email", {children: []});
     const image_stubber = make_image_stubber();
-    const base_url = window.location.href;
     handler.call(target, e);
 
     const avatar_img = image_stubber.get(0);
-    const expected_url = new URL("avatar/42/medium?v=" + alice.avatar_version, base_url);
-    assert.equal(avatar_img.src.toString(), expected_url.toString());
+    assert.equal(avatar_img.src.toString(), "/avatar/42/medium");
 
     // todo: load image
 });
diff --git a/static/js/people.js b/static/js/people.js
index 2aeec140ea..2ec6d19646 100644
--- a/static/js/people.js
+++ b/static/js/people.js
@@ -659,6 +659,26 @@ export function small_avatar_url_for_person(person) {
     return format_small_avatar_url("/avatar/" + person.user_id);
 }
 
+function medium_gravatar_url_for_email(email) {
+    const hash = md5(email.toLowerCase());
+    const avatar_url = "https://secure.gravatar.com/avatar/" + hash + "?d=identicon";
+    const url = new URL(avatar_url, location);
+    url.search += (url.search ? "&" : "") + "s=500";
+    return url.href;
+}
+
+export function medium_avatar_url_for_person(person) {
+    /* Unlike the small avatar URL case, we don't generally have a
+     * medium avatar URL included in person objects. So only have the
+     * gravatar and server endpoints here. */
+
+    if (person.avatar_url === null) {
+        return medium_gravatar_url_for_email(person.email);
+    }
+
+    return "/avatar/" + person.user_id + "/medium";
+}
+
 export function sender_info_for_recent_topics_row(sender_ids) {
     const senders_info = [];
     for (const id of sender_ids) {
diff --git a/static/js/popovers.js b/static/js/popovers.js
index dcf198dc0e..78a7208659 100644
--- a/static/js/popovers.js
+++ b/static/js/popovers.js
@@ -158,8 +158,7 @@ function init_email_tooltip(user) {
 }
 
 function load_medium_avatar(user, elt) {
-    const avatar_path = "avatar/" + user.user_id + "/medium?v=" + user.avatar_version;
-    const user_avatar_url = new URL(avatar_path, window.location.href);
+    const user_avatar_url = people.medium_avatar_url_for_person(user);
     const sender_avatar_medium = new Image();
 
     sender_avatar_medium.src = user_avatar_url;
diff --git a/static/js/user_profile.js b/static/js/user_profile.js
index e4fee6e089..dd7b2ed3c1 100644
--- a/static/js/user_profile.js
+++ b/static/js/user_profile.js
@@ -154,7 +154,7 @@ export function show_user_profile(user) {
         full_name: user.full_name,
         email: people.get_visible_email(user),
         profile_data,
-        user_avatar: "avatar/" + user.user_id + "/medium",
+        user_avatar: people.medium_avatar_url_for_person(user),
         is_me: people.is_current_user(user.email),
         date_joined: dateFormat.format(parseISO(user.date_joined)),
         last_seen: buddy_data.user_last_seen_time_status(user.user_id),