diff --git a/includes/compat.php b/includes/compat.php
index 4bee640..3dd405c 100644
--- a/includes/compat.php
+++ b/includes/compat.php
@@ -35,3 +35,15 @@ if ( ! function_exists( 'get_self_link' ) ) {
 		return esc_url( apply_filters( 'self_link', set_url_scheme( 'http://' . $host['host'] . $path ) ) );
 	}
 }
+
+if ( ! function_exists( 'is_countable' ) ) {
+	/**
+	 * Polyfill for `is_countable()` function added in PHP 7.3.
+	 *
+	 * @param mixed $value The value to check.
+	 * @return bool True if `$value` is countable, otherwise false.
+	 */
+	function is_countable( $value ) {
+			return is_array( $value ) || $value instanceof \Countable;
+	}
+}
diff --git a/includes/rest/class-collection.php b/includes/rest/class-collection.php
index 2e6522e..365641c 100644
--- a/includes/rest/class-collection.php
+++ b/includes/rest/class-collection.php
@@ -105,7 +105,7 @@ class Collection {
 			'@context'   => Activity::CONTEXT,
 			'id'         => get_rest_url_by_path( sprintf( 'users/%d/collections/tags', $user->get__id() ) ),
 			'type'       => 'Collection',
-			'totalItems' => count( $tags ),
+			'totalItems' => is_countable( $tags ) ? count( $tags ) : 0,
 			'items'      => array(),
 		);
 
@@ -163,7 +163,7 @@ class Collection {
 			'@context'     => Activity::CONTEXT,
 			'id'           => get_rest_url_by_path( sprintf( 'users/%d/collections/featured', $user_id ) ),
 			'type'         => 'OrderedCollection',
-			'totalItems'   => count( $posts ),
+			'totalItems'   => is_countable( $posts ) ? count( $posts ) : 0,
 			'orderedItems' => array(),
 		);
 
diff --git a/includes/rest/class-following.php b/includes/rest/class-following.php
index 22c9d46..58e4375 100644
--- a/includes/rest/class-following.php
+++ b/includes/rest/class-following.php
@@ -75,7 +75,7 @@ class Following {
 
 		$items = apply_filters( 'activitypub_rest_following', array(), $user ); // phpcs:ignore
 
-		$json->totalItems = count( $items ); // phpcs:ignore
+		$json->totalItems = is_countable( $items ) ? count( $items ) : 0; // phpcs:ignore
 		$json->orderedItems = $items; // phpcs:ignore
 
 		$json->first = $json->partOf; // phpcs:ignore
diff --git a/includes/rest/class-nodeinfo.php b/includes/rest/class-nodeinfo.php
index 1f6277a..4829e75 100644
--- a/includes/rest/class-nodeinfo.php
+++ b/includes/rest/class-nodeinfo.php
@@ -88,7 +88,7 @@ class Nodeinfo {
 			)
 		);
 
-		if ( is_array( $users ) ) {
+		if ( is_countable( $users ) ) {
 			$users = count( $users );
 		} else {
 			$users = 1;
@@ -145,7 +145,7 @@ class Nodeinfo {
 			)
 		);
 
-		if ( is_array( $users ) ) {
+		if ( is_countable( $users ) ) {
 			$users = count( $users );
 		} else {
 			$users = 1;
diff --git a/includes/transformer/class-post.php b/includes/transformer/class-post.php
index 9250afe..36d357e 100644
--- a/includes/transformer/class-post.php
+++ b/includes/transformer/class-post.php
@@ -335,6 +335,8 @@ class Post {
 			return \ucfirst( \get_option( 'activitypub_object_type', 'note' ) );
 		}
 
+		// Default to Article.
+		$object_type = 'Article';
 		$post_type = \get_post_type( $this->wp_post );
 		switch ( $post_type ) {
 			case 'post':