diff --git a/src/wp-admin/includes/bookmark.php b/src/wp-admin/includes/bookmark.php
index 6cc6683f029a4..f1c7f77aa0a1f 100644
--- a/src/wp-admin/includes/bookmark.php
+++ b/src/wp-admin/includes/bookmark.php
@@ -126,7 +126,12 @@ function wp_delete_link( $link_id ) {
  */
 function wp_get_link_cats( $link_id = 0 ) {
 	$cats = wp_get_object_terms( $link_id, 'link_category', array( 'fields' => 'ids' ) );
-	return array_unique( $cats );
+
+	if ( is_array( $cats ) ) {
+		return array_unique( $cats );
+	}
+
+	return array();
 }
 
 /**
@@ -307,16 +312,17 @@ function wp_update_link( $linkdata ) {
 	$link = wp_slash( $link );
 
 	// Passed link category list overwrites existing category list if not empty.
-	if ( isset( $linkdata['link_category'] ) && is_array( $linkdata['link_category'] )
-		&& count( $linkdata['link_category'] ) > 0
-	) {
+	$link_cats = null;
+	if ( ! empty( $linkdata['link_category'] ) && is_array( $linkdata['link_category'] ) ) {
 		$link_cats = $linkdata['link_category'];
-	} else {
+	} elseif ( ! empty( $link['link_category'] )  && is_array( $link['link_category'] ) ) {
 		$link_cats = $link['link_category'];
 	}
 
 	// Merge old and new fields with new fields overwriting old ones.
-	$linkdata                  = array_merge( $link, $linkdata );
+	if ( ! empty( $link ) && is_array( $link ) ) {
+		$linkdata = array_merge( $link, $linkdata );
+	}
 	$linkdata['link_category'] = $link_cats;
 
 	return wp_insert_link( $linkdata );
diff --git a/tests/phpunit/tests/bookmark/getBookmarks.php b/tests/phpunit/tests/bookmark/getBookmarks.php
index 9200ed9d09094..649a66bd0ab44 100644
--- a/tests/phpunit/tests/bookmark/getBookmarks.php
+++ b/tests/phpunit/tests/bookmark/getBookmarks.php
@@ -2,8 +2,10 @@
 
 /**
  * @group bookmark
+ * @covers ::get_bookmarks
  */
 class Tests_Bookmark_GetBookmarks extends WP_UnitTestCase {
+
 	public function test_should_hit_cache() {
 		global $wpdb;
 
diff --git a/tests/phpunit/tests/bookmark/wpUpdateLink.php b/tests/phpunit/tests/bookmark/wpUpdateLink.php
new file mode 100644
index 0000000000000..dc28e87c66b84
--- /dev/null
+++ b/tests/phpunit/tests/bookmark/wpUpdateLink.php
@@ -0,0 +1,34 @@
+<?php
+
+/**
+ * @group bookmark
+ * @covers ::wp_update_link
+ */
+class Tests_Bookmark_WpUpdateLink extends WP_UnitTestCase {
+
+	public function test_should_update_existing_bookmark() {
+		$bookmark_id = self::factory()->bookmark->create();
+		$link_name   = 'foo';
+		$result      = wp_update_link(
+			array(
+				'link_id'   => $bookmark_id,
+				'link_name' => $link_name,
+			)
+		);
+		$this->assertSame( $bookmark_id, $result );
+		$this->assertSame( $link_name, get_bookmark( $bookmark_id )->link_name );
+	}
+
+	public function test_should_not_update_non_existing_bookmark() {
+		$bookmark_id = -1;
+		$link_name   = 'foo';
+		$result      = wp_update_link(
+			array(
+				'link_id'   => $bookmark_id,
+				'link_name' => $link_name,
+			)
+		);
+		$this->assertNotSame( $bookmark_id, $result );
+		$this->assertWPError( $result );
+	}
+}