diff --git a/HeaderUtils.php b/HeaderUtils.php
index f91c7e1d9..3456edace 100644
--- a/HeaderUtils.php
+++ b/HeaderUtils.php
@@ -256,7 +256,7 @@ public static function parseQuery(string $query, bool $ignoreBrackets = false, s
     private static function groupParts(array $matches, string $separators, bool $first = true): array
     {
         $separator = $separators[0];
-        $separators = substr($separators, 1);
+        $separators = substr($separators, 1) ?: '';
         $i = 0;
 
         if ('' === $separators && !$first) {
diff --git a/Session/Storage/Handler/PdoSessionHandler.php b/Session/Storage/Handler/PdoSessionHandler.php
index a40a7bc77..1e8f9c6c4 100644
--- a/Session/Storage/Handler/PdoSessionHandler.php
+++ b/Session/Storage/Handler/PdoSessionHandler.php
@@ -90,12 +90,12 @@ class PdoSessionHandler extends AbstractSessionHandler
     /**
      * Username when lazy-connect.
      */
-    private string $username = '';
+    private ?string $username = null;
 
     /**
      * Password when lazy-connect.
      */
-    private string $password = '';
+    private ?string $password = null;
 
     /**
      * Connection options when lazy-connect.