diff --git a/dictionaries/CallMap.php b/dictionaries/CallMap.php
index 7bd9231d8..fa46c2182 100644
--- a/dictionaries/CallMap.php
+++ b/dictionaries/CallMap.php
@@ -4395,7 +4395,7 @@ return [
 'HRTime\StopWatch::stop' => ['void'],
 'html_entity_decode' => ['string', 'string'=>'string', 'flags='=>'int', 'encoding='=>'string'],
 'htmlentities' => ['string', 'string'=>'string', 'flags='=>'int', 'encoding='=>'string', 'double_encode='=>'bool'],
-'htmlspecialchars' => ['string', 'string'=>'string', 'flags='=>'int', 'encoding='=>'string', 'double_encode='=>'bool'],
+'htmlspecialchars' => ['string', 'string'=>'string', 'flags='=>'int', 'encoding='=>'string|null', 'double_encode='=>'bool'],
 'htmlspecialchars_decode' => ['string', 'string'=>'string', 'flags='=>'int'],
 'http\Client::__construct' => ['void', 'driver='=>'string', 'persistent_handle_id='=>'string'],
 'http\Client::addCookies' => ['http\Client', 'cookies='=>'?array'],
diff --git a/stubs/CoreGenericFunctions.phpstub b/stubs/CoreGenericFunctions.phpstub
index 4236bcb9c..c4aacdf7b 100644
--- a/stubs/CoreGenericFunctions.phpstub
+++ b/stubs/CoreGenericFunctions.phpstub
@@ -690,7 +690,7 @@ function html_entity_decode(string $string, ?int $quote_style = null, ?string $c
  *     : string
  * )
  */
-function htmlspecialchars(string $string, int $flags = ENT_COMPAT | ENT_HTML401, string $encoding = 'UTF-8', bool $double_encode = true) : string {}
+function htmlspecialchars(string $string, int $flags = ENT_COMPAT | ENT_HTML401, ?string $encoding = 'UTF-8', bool $double_encode = true) : string {}
 
 /**
  * @psalm-pure