diff --git a/system/Cache/Handlers/BaseHandler.php b/system/Cache/Handlers/BaseHandler.php
index 7d7b936940e8..3cf8f38702a6 100644
--- a/system/Cache/Handlers/BaseHandler.php
+++ b/system/Cache/Handlers/BaseHandler.php
@@ -64,9 +64,9 @@ public static function validateKey($key, $prefix = ''): string
 		{
 			throw new InvalidArgumentException('Cache key cannot be empty.');
 		}
-		if (strpbrk($key, self::RESERVED_CHARACTERS) !== false)
+		if (strpbrk($key, static::RESERVED_CHARACTERS) !== false)
 		{
-			throw new InvalidArgumentException('Cache key contains reserved characters ' . self::RESERVED_CHARACTERS);
+			throw new InvalidArgumentException('Cache key contains reserved characters ' . static::RESERVED_CHARACTERS);
 		}
 
 		// If the key with prefix exceeds the length then return the hashed version
diff --git a/system/Cache/Handlers/FileHandler.php b/system/Cache/Handlers/FileHandler.php
index 95bdfa0995b8..7f70cc848ec2 100644
--- a/system/Cache/Handlers/FileHandler.php
+++ b/system/Cache/Handlers/FileHandler.php
@@ -20,6 +20,12 @@
  */
 class FileHandler extends BaseHandler
 {
+	/**
+	 * Reserved characters that cannot be used in a key or tag.
+	 * From https://github.com/symfony/cache-contracts/blob/c0446463729b89dd4fa62e9aeecc80287323615d/ItemInterface.php#L43
+	 */
+	public const RESERVED_CHARACTERS = '{}()\@:';
+
 	/**
 	 * Maximum key length.
 	 *