diff --git a/includes/class-activitypub.php b/includes/class-activitypub.php
index 7bf9fab..baf7d67 100644
--- a/includes/class-activitypub.php
+++ b/includes/class-activitypub.php
@@ -19,9 +19,9 @@ class Activitypub {
 		add_post_type_support( 'post', 'activitypub' );
 		add_post_type_support( 'page', 'activitypub' );
 
-		$post_types = get_post_types_by_support( 'activitypub' );
 		add_action( 'transition_post_status', array( '\Activitypub\Activitypub', 'schedule_post_activity' ), 10, 3 );
 	}
+
 	/**
 	 * Return a AS2 JSON version of an author, post or page
 	 *
@@ -99,6 +99,12 @@ class Activitypub {
 			return;
 		}
 
+		// check if post-type supports ActivityPub
+		$post_types = get_post_types_by_support( 'activitypub' );
+		if ( ! in_array( $post->post_type, $post_types, true ) ) {
+			return;
+		}
+
 		if ( 'publish' === $new_status && 'publish' !== $old_status ) {
 			wp_schedule_single_event( time() + wp_rand( 0, 120 ), 'activitypub_send_post_activity', array( $post->ID ) );
 		} elseif ( 'publish' === $new_status ) {