diff --git a/phpstan_baseline.neon b/phpstan_baseline.neon
index 38cd3fa..f45121d 100644
--- a/phpstan_baseline.neon
+++ b/phpstan_baseline.neon
@@ -25,11 +25,6 @@ parameters:
 			count: 1
 			path: src/PHPCodeBrowser/IssueXML.php
 
-		-
-			message: "#^Only booleans are allowed in an if condition, mixed given\\.$#"
-			count: 1
-			path: src/PHPCodeBrowser/IssueXML.php
-
 		-
 			message: "#^Only booleans are allowed in a negated boolean, string given\\.$#"
 			count: 1
diff --git a/src/PHPCodeBrowser/IssueXML.php b/src/PHPCodeBrowser/IssueXML.php
index 0afd8b0..1911f1b 100644
--- a/src/PHPCodeBrowser/IssueXML.php
+++ b/src/PHPCodeBrowser/IssueXML.php
@@ -56,6 +56,7 @@
 namespace PHPCodeBrowser;
 
 use DOMDocument;
+use DOMDocumentType;
 use DOMNode;
 use DOMNodeList;
 use DOMXPath;
@@ -155,6 +156,10 @@ public function addDirectory(string $directory): IssueXML
     public function addXMLFile(DOMDocument $domDocument): void
     {
         foreach ($domDocument->childNodes as $node) {
+            if ($node instanceof DOMDocumentType) {
+                continue;
+            }
+
             $this->documentElement->appendChild($this->importNode($node, true));
         }
     }