diff --git a/HealthCheck/Tools/class-health-check-debug-log-viewer.php b/HealthCheck/Tools/class-health-check-debug-log-viewer.php
index 825e4a5..c3bc67f 100644
--- a/HealthCheck/Tools/class-health-check-debug-log-viewer.php
+++ b/HealthCheck/Tools/class-health-check-debug-log-viewer.php
@@ -11,7 +11,7 @@ public function __construct() {
 
 	private function read_debug_log() {
 		if ( ! defined( 'WP_DEBUG_LOG' ) || false === WP_DEBUG_LOG ) {
-			return null;
+			return '';
 		}
 
 		$logfile = WP_DEBUG_LOG;
@@ -25,7 +25,7 @@ private function read_debug_log() {
 		}
 
 		if ( ! file_exists( $logfile ) ) {
-			return null;
+			return '';
 		}
 
 		$debug_log = @file_get_contents( $logfile );