diff --git a/src/wp-includes/comment-template.php b/src/wp-includes/comment-template.php
index 79b51c1a98..f8ebaecdcc 100644
--- a/src/wp-includes/comment-template.php
+++ b/src/wp-includes/comment-template.php
@@ -433,10 +433,13 @@ function comment_class( $class = '', $comment = null, $post_id = null, $echo = t
 function get_comment_class( $class = '', $comment_id = null, $post_id = null ) {
 	global $comment_alt, $comment_depth, $comment_thread_alt;
 
-	$comment = get_comment($comment_id);
-
 	$classes = array();
 
+	$comment = get_comment( $comment_id );
+	if ( ! $comment ) {
+		return $classes;
+	}
+
 	// Get the comment type (comment, trackback),
 	$classes[] = ( empty( $comment->comment_type ) ) ? 'comment' : $comment->comment_type;
 
diff --git a/tests/phpunit/tests/comment/getCommentClass.php b/tests/phpunit/tests/comment/getCommentClass.php
index c7ce64923b..5ca3bc41ea 100644
--- a/tests/phpunit/tests/comment/getCommentClass.php
+++ b/tests/phpunit/tests/comment/getCommentClass.php
@@ -36,4 +36,11 @@ class Tests_Comment_GetCommentClass extends WP_UnitTestCase {
 		$this->assertContains( 'foo', $classes );
 		$this->assertContains( 'bar', $classes );
 	}
+
+	/**
+	 * @ticket 33947
+	 */
+	public function test_should_return_an_empty_array_for_invalid_comment_id() {
+		$this->assertSame( array(), get_comment_class( 'foo', 12345 ) );
+	}
 }