diff --git a/inc/activities/create.php b/inc/activities/create.php
index d5920ae..7a8e415 100644
--- a/inc/activities/create.php
+++ b/inc/activities/create.php
@@ -12,45 +12,48 @@ to the object and vice-versa.
 Returns either the modified $activity or a WP_Error.
 */
 function handle( $actor, $activity ) {
-    if ( !(array_key_exists( "type", $activity ) && $activity["type"] === "Create") ) {
-        return new WP_Error(
+    if ( !(array_key_exists( 'type', $activity ) && $activity['type'] === 'Create') ) {
+        return new \WP_Error(
             'invalid_activity', __( 'Expecting a Create activity', 'activitypub' )
         );
     }
-    if ( !array_key_exists( "object", $activity ) ) {
-        return new WP_Error(
+    if ( !array_key_exists( 'object', $activity ) ) {
+        return new \WP_Error(
             'invalid_object', __( 'Expecting an object', 'activitypub' )
         );
     }
-    if ( !array_key_exists( "actor", $activity ) ) {
-        // TODO validate that $activity["actor"] is the URL of the $actor
-        return new WP_Error(
+    if ( !array_key_exists( 'actor', $activity ) ) {
+        // TODO validate that $activity['actor'] is the URL of the $actor
+        return new \WP_Error(
             'invalid_actor', __( 'Expecting a valid actor', 'activitypub' )
         );
     }
-    $object = $activity["object"];
-    $actor_id = $activity["actor"];
-    $object["attributedTo"] = $actor_id;
+    $object = $activity['object'];
+    $actor_id = $activity['actor'];
+    $object['attributedTo'] = $actor_id;
     reconcile_receivers( $object, $activity );
     scrub_object( $object );
-    $object = \objects\persist_object( $object );
-    $activity["object"] = $object;
+    $object = \objects\create_object( $object );
+    if ( is_wp_error( $object ) ) {
+        return $object;
+    }
+    $activity['object'] = $object;
     return $activity;
 }
 
 function reconcile_receivers( &$object, &$activity ) {
-    copy_field_value( "audience", $object, $activity );
-    copy_field_value( "audience", $activity, $object );
+    copy_field_value( 'audience', $object, $activity );
+    copy_field_value( 'audience', $activity, $object );
 
-    copy_field_value( "to", $object, $activity );
-    copy_field_value( "to", $activity, $object );
+    copy_field_value( 'to', $object, $activity );
+    copy_field_value( 'to', $activity, $object );
 
-    copy_field_value( "cc", $object, $activity );
-    copy_field_value( "cc", $activity, $object );
+    copy_field_value( 'cc', $object, $activity );
+    copy_field_value( 'cc', $activity, $object );
 
     // copy bcc and bto to activity for delivery but not to object
-    copy_field_value( "bcc", $object, $activity );
-    copy_field_value( "bto", $object, $activity );
+    copy_field_value( 'bcc', $object, $activity );
+    copy_field_value( 'bto', $object, $activity );
 }
 
 function copy_field_value( $field, $from, &$to ) {
@@ -66,7 +69,7 @@ function copy_field_value( $field, $from, &$to ) {
 }
 
 function scrub_object( &$object ) {
-    unset( $object["bcc"] );
-    unset( $object["bto"] );
+    unset( $object['bcc'] );
+    unset( $object['bto'] );
 }
 ?>
diff --git a/inc/activities/update.php b/inc/activities/update.php
index 54f82ef..a92cc39 100644
--- a/inc/activities/update.php
+++ b/inc/activities/update.php
@@ -1,7 +1,40 @@
 <?php
 namespace \activities\update;
 
-function handle( $actor, $activity ) {
+require_once plugin_dir_path( __FILE __ ) . '/../objects.php';
 
+function handle( $actor, $activity ) {
+    if ( !(array_key_exists( 'type', $activity ) && $activity['type'] === 'Update') ) {
+        return new \WP_Error(
+            'invalid_activity',
+            __( 'Expecting an Update activity', 'activitypub' ),
+            array( 'status' => 400 )
+        );
+    }
+    if ( !array_key_exists( 'object', $activity ) ) {
+        return new \WP_Error(
+            'invalid_activity',
+            __( 'Expecting an object', 'activitypub' )
+            array( 'status' => 400 )
+        );
+    }
+    $update_object = $activity['object'];
+    if ( !array_key_exists( 'id', $update_object ) ) {
+        return new \WP_Error(
+            'invalid_object',
+            __( 'Object must have an "id" parameter', 'activitypub' )
+            array( 'status' => 400 )
+        );
+    }
+    $existing_object = \objects\get_object_from_url( $update_object['id'] );
+    if ( is_wp_error( $existing_object ) ) {
+        return $existing_object;
+    }
+    $updated_object = array_merge( $existing_object, $update_object );
+    $updated_object = \objects\update_object( $updated_object );
+    if ( is_wp_error( $updated_object ) ) {
+        return $updated_object;
+    }
+    return $activity;
 }
 ?>
diff --git a/inc/objects.php b/inc/objects.php
index 81ab117..120f58c 100644
--- a/inc/objects.php
+++ b/inc/objects.php
@@ -1,13 +1,44 @@
 <?php
 namespace objects;
 
-function persist_object( $object ) {
+function create_object( $object ) {
     global $wpdb;
-    $wpdb->insert( 'activitypub_objects', array( 'object' => wp_json_encode( $object ) ) );
+    $res = $wpdb->insert(
+        'activitypub_objects', array( 'object' => wp_json_encode( $object ) )
+    );
+    if ( !$res ) {
+        return new \WP_Error(
+            'db_error', __( 'Failed to insert object row', 'activitypub' )
+        );
+    }
     $object['id'] = get_object_url( $wpdb->insert_id );
     return $object;
 }
 
+function update_object( $object ) {
+    global $wpdb;
+    if ( !array_key_exists( 'id', $object ) ) {
+        return new \WP_Error(
+            'invalid_object',
+            __( 'Object must have an "id" parameter', 'activitypub' ),
+            array( 'status' => 400 )
+        );
+    }
+    $id = get_id_from_url( $object['id'] );
+    $object_json = wp_json_encode( $object );
+    $res = $wpdb->update(
+        'activitypub_object',
+        array( 'object' => $object_json ),
+        array( 'id' => $id ),
+        '%s', '%d' );
+    if ( !$res ) {
+        return new \WP_Error(
+            'db_error', __( 'Failed to update object row', 'activitypub' )
+        );
+    }
+    return $object;
+}
+
 function get_object( $id ) {
     global $wpdb;
     $object_json = $wpdb->get_var( sprintf(
@@ -15,7 +46,7 @@ function get_object( $id ) {
     ) ); 
     if ( is_null( $object_json ) ) {
         return new \WP_Error(
-            404, __( 'Object not found', 'activitypub' ), array ( 'status' => 404 )
+            'not_found', __( 'Object not found', 'activitypub' ), array ( 'status' => 404 )
         );
     }
     $object = json_decode( $object_json, true );
@@ -23,6 +54,26 @@ function get_object( $id ) {
     return $object;
 }
 
+function get_id_from_url( $url ) {
+    global $wpdb;
+    $matches = array();
+    $found = preg_match(
+        get_rest_url( null, '/activitypub/v1/object/(.+)' ), $url, $matches );
+    if ( $found === 0 || count( $matches ) != 2 ) {
+        return new \WP_Error(
+            'invalid_url',
+            sprintf( '%s %s', $url, __( 'is not a valid object url', 'activitypub' ) ),
+            array( 'status' => 400 )
+        );
+    }
+    $id = $matches[1];
+    return $id;
+}
+
+function get_object_from_url( $url ) {
+    return get_object( get_id_from_url( $url ) );
+}
+
 function get_object_url( $id ) {
     return get_rest_url( null, sprintf( '/activitypub/v1/object/%d', $id ) );
 }