diff --git a/lib/federation-setup.js b/lib/federation-setup.js
index 5461b35..608ca5f 100644
--- a/lib/federation-setup.js
+++ b/lib/federation-setup.js
@@ -721,6 +721,20 @@ export async function buildPersonActor(
     personOptions.assertionMethods = keyPairs.map((k) => k.multikey);
   }
 
+  // Build profile field attachments (PropertyValue).
+  // Always include a "Fediverse" field with the actor's handle — this serves
+  // two purposes: (1) shows the canonical fediverse address on the profile,
+  // and (2) ensures 2+ attachments when combined with user-defined fields,
+  // preventing Fedify's JSON-LD compaction from collapsing single-element
+  // arrays to plain objects (which Mastodon's update_account_fields rejects).
+  const actorUrl = ctx.getActorUri(identifier)?.href;
+  const fediverseField = actorUrl
+    ? new PropertyValue({
+        name: "Fediverse",
+        value: `<a href="${actorUrl}" rel="me">@${identifier}@${new URL(actorUrl).hostname}</a>`,
+      })
+    : null;
+
   if (profile.attachments?.length > 0) {
     personOptions.attachments = profile.attachments.map(
       (att) =>
@@ -729,6 +743,12 @@ export async function buildPersonActor(
           value: formatAttachmentValue(att.value),
         }),
     );
+    // Append fediverse field if not already present in user-defined fields
+    if (fediverseField && !profile.attachments.some((a) => a.name === "Fediverse")) {
+      personOptions.attachments.push(fediverseField);
+    }
+  } else if (fediverseField) {
+    personOptions.attachments = [fediverseField];
   }
 
   if (profile.alsoKnownAs?.length > 0) {
diff --git a/package.json b/package.json
index 779baca..9c0d3e7 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@rmdes/indiekit-endpoint-activitypub",
-  "version": "2.0.21",
+  "version": "2.0.22",
   "description": "ActivityPub federation endpoint for Indiekit via Fedify. Adds full fediverse support: actor, inbox, outbox, followers, following, syndication, and Mastodon migration.",
   "keywords": [
     "indiekit",