diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index f195fa9f8..4f4d5ab8f 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -10,7 +10,6 @@ parameters:
 		- src/
 	ignoreErrors:
 		- '#^PHPDoc tag @throws with type AmpProject\\Exception\\FailedRemoteRequest is not subtype of Throwable$#'
-		- '#^Parameter \#1 (\$exception_handler|\$callback) of function set_exception_handler expects#'
 	excludePaths:
 		analyse:
 			- src/FakeEnum.php
diff --git a/src/Cli/Options.php b/src/Cli/Options.php
index ff5a234be..5efd264f4 100644
--- a/src/Cli/Options.php
+++ b/src/Cli/Options.php
@@ -535,6 +535,7 @@ public function help()
      */
     private function readPHPArgv()
     {
+        /** @var list<string>|null $argv */
         global $argv;
 
         if (is_array($argv)) {
diff --git a/src/Dom/Document/Filter/DeduplicateTag.php b/src/Dom/Document/Filter/DeduplicateTag.php
index a0a87f1d1..db0106031 100644
--- a/src/Dom/Document/Filter/DeduplicateTag.php
+++ b/src/Dom/Document/Filter/DeduplicateTag.php
@@ -71,9 +71,7 @@ public function afterLoad(Document $document)
             }
 
             // Avoid doing the above query again if possible.
-            if (in_array($tagName, [Tag::HEAD, Tag::BODY], true)) {
-                $document->$tagName = $mainTag;
-            }
+            $document->$tagName = $mainTag;
         }
     }
 }
diff --git a/src/Dom/Document/Filter/MustacheScriptTemplates.php b/src/Dom/Document/Filter/MustacheScriptTemplates.php
index 800c403aa..248811738 100644
--- a/src/Dom/Document/Filter/MustacheScriptTemplates.php
+++ b/src/Dom/Document/Filter/MustacheScriptTemplates.php
@@ -8,6 +8,7 @@
 use AmpProject\Dom\Document\BeforeLoadFilter;
 use AmpProject\Dom\Document\BeforeSaveFilter;
 use AmpProject\Html\Tag;
+use DOMElement;
 
 /**
  * Filter to handle the script[template="amp-mustache"].
@@ -128,8 +129,9 @@ static function ($matches) use ($mustacheTagPlaceholders) {
                     // unterminated entity reference "baz". When the attribute value is updated via setAttribute() this
                     // same problem does not occur, so that is why the following is used.
 
-                    // @phpstan-ignore method.notFound
-                    $attribute->parentNode->setAttribute($attribute->nodeName, $value);
+                    if ($attribute->parentNode instanceof DOMElement) {
+                        $attribute->parentNode->setAttribute($attribute->nodeName, $value);
+                    }
 
                     $this->mustacheTagsReplaced = true;
                 }
diff --git a/src/RemoteRequest/TemporaryFileCachedRemoteGetRequest.php b/src/RemoteRequest/TemporaryFileCachedRemoteGetRequest.php
index bf534f560..b9f8d80e8 100644
--- a/src/RemoteRequest/TemporaryFileCachedRemoteGetRequest.php
+++ b/src/RemoteRequest/TemporaryFileCachedRemoteGetRequest.php
@@ -86,7 +86,7 @@ public function get($url, $headers = [])
 
         // phpcs:disable PHPCompatibility.FunctionUse.NewFunctionParameters.unserialize_optionsFound
         if ($cachedResponse !== false) {
-            $cachedResponse = unserialize($cachedResponse, [RemoteGetRequestResponse::class]);
+            $cachedResponse = unserialize($cachedResponse, ['allowed_classes' => [RemoteGetRequestResponse::class]]);
         }
         // phpcs:enable PHPCompatibility.FunctionUse.NewFunctionParameters.unserialize_optionsFound