diff --git a/plugins/ActivityPub/ActivityPubPlugin.php b/plugins/ActivityPub/ActivityPubPlugin.php
index bba73b13cd..6d5e6fc652 100644
--- a/plugins/ActivityPub/ActivityPubPlugin.php
+++ b/plugins/ActivityPub/ActivityPubPlugin.php
@@ -36,7 +36,6 @@ foreach (glob(__DIR__ . DIRECTORY_SEPARATOR . 'lib' . DIRECTORY_SEPARATOR . 'mod
 }
 
 // So that this isn't hardcoded everywhere
-define('ACTIVITYPUB_BASE_ACTOR_URI', common_root_url().'index.php/user/');
 const ACTIVITYPUB_PUBLIC_TO = ['https://www.w3.org/ns/activitystreams#Public',
                                'Public',
                                'as:Public'
@@ -67,11 +66,7 @@ class ActivityPubPlugin extends Plugin
      */
     public static function actor_uri($profile)
     {
-        if ($profile->isLocal()) {
-            return ACTIVITYPUB_BASE_ACTOR_URI.$profile->getID();
-        } else {
-            return $profile->getUri();
-        }
+        return common_profile_uri($profile);
     }
 
     /**
diff --git a/plugins/ActivityPub/lib/explorer.php b/plugins/ActivityPub/lib/explorer.php
index 7b1b2d5b6e..098f822719 100644
--- a/plugins/ActivityPub/lib/explorer.php
+++ b/plugins/ActivityPub/lib/explorer.php
@@ -180,8 +180,9 @@ class Activitypub_explorer
             common_debug('ActivityPub Explorer: Unable to find a local Aprofile for ' . $uri . ' - looking for a Profile instead.');
             // Well, maybe it is a pure blood?
             // Iff, we are in the same instance:
-            $ACTIVITYPUB_BASE_ACTOR_URI_length = strlen(ACTIVITYPUB_BASE_ACTOR_URI);
-            if (substr($uri, 0, $ACTIVITYPUB_BASE_ACTOR_URI_length) == ACTIVITYPUB_BASE_ACTOR_URI) {
+            $ACTIVITYPUB_BASE_ACTOR_URI = common_local_url('userbyid', ['id' => null], null, null, false, true); // @FIXME: Could this be too hardcoded?
+            $ACTIVITYPUB_BASE_ACTOR_URI_length = strlen($ACTIVITYPUB_BASE_ACTOR_URI);
+            if (substr($uri, 0, $ACTIVITYPUB_BASE_ACTOR_URI_length) === $ACTIVITYPUB_BASE_ACTOR_URI) {
                 try {
                     $profile = Profile::getByID((int)substr($uri, $ACTIVITYPUB_BASE_ACTOR_URI_length));
                     common_debug('ActivityPub Explorer: Found a Profile for ' . $uri);