[ci skip] Fix #4928
diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index 71656be..c9cb5c8 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -67,7 +67,10 @@
 		require_once(APPPATH.'config/'.ENVIRONMENT.'/constants.php');
 	}
 
-	require_once(APPPATH.'config/constants.php');
+	if (file_exists(APPPATH.'config/constants.php'))
+	{
+		require_once(APPPATH.'config/constants.php');
+	}
 
 /*
  * ------------------------------------------------------