diff --git a/src/Symfony/Component/String/AbstractString.php b/src/Symfony/Component/String/AbstractString.php
index 435363b798d25..e56697e391549 100644
--- a/src/Symfony/Component/String/AbstractString.php
+++ b/src/Symfony/Component/String/AbstractString.php
@@ -692,6 +692,11 @@ public function wordwrap(int $width = 75, string $break = "\n", bool $cut = fals
         return $str;
     }
 
+    public function __sleep(): array
+    {
+        return ['string'];
+    }
+
     public function __clone()
     {
         $this->ignoreCase = false;
diff --git a/src/Symfony/Component/String/UnicodeString.php b/src/Symfony/Component/String/UnicodeString.php
index 61e8c008dcb35..d7df6f5e1400b 100644
--- a/src/Symfony/Component/String/UnicodeString.php
+++ b/src/Symfony/Component/String/UnicodeString.php
@@ -347,6 +347,11 @@ public function startsWith($prefix): bool
         return $prefix === grapheme_extract($this->string, \strlen($prefix), GRAPHEME_EXTR_MAXBYTES);
     }
 
+    public function __wakeup()
+    {
+        normalizer_is_normalized($this->string) ?: $this->string = normalizer_normalize($this->string);
+    }
+
     public function __clone()
     {
         if (null === $this->ignoreCase) {