diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..723ef36
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+.idea
\ No newline at end of file
diff --git a/tcpdf.php b/tcpdf.php
index ab5e138..563d6d8 100644
--- a/tcpdf.php
+++ b/tcpdf.php
@@ -9638,6 +9638,16 @@ class TCPDF {
 		$xmp .= "\t\t\t\t\t\t".'<pdfaSchema:namespaceURI>http://ns.adobe.com/pdf/1.3/</pdfaSchema:namespaceURI>'."\n";
 		$xmp .= "\t\t\t\t\t\t".'<pdfaSchema:prefix>pdf</pdfaSchema:prefix>'."\n";
 		$xmp .= "\t\t\t\t\t\t".'<pdfaSchema:schema>Adobe PDF Schema</pdfaSchema:schema>'."\n";
+        $xmp .= "\t\t\t\t\t\t".'<pdfaSchema:property>'."\n";
+        $xmp .= "\t\t\t\t\t\t\t".'<rdf:Seq>'."\n";
+        $xmp .= "\t\t\t\t\t\t\t\t".'<rdf:li rdf:parseType="Resource">'."\n";
+        $xmp .= "\t\t\t\t\t\t\t\t\t".'<pdfaProperty:category>internal</pdfaProperty:category>'."\n";
+        $xmp .= "\t\t\t\t\t\t\t\t\t".'<pdfaProperty:description>Adobe PDF Schema</pdfaProperty:description>'."\n";
+        $xmp .= "\t\t\t\t\t\t\t\t\t".'<pdfaProperty:name>InstanceID</pdfaProperty:name>'."\n";
+        $xmp .= "\t\t\t\t\t\t\t\t\t".'<pdfaProperty:valueType>URI</pdfaProperty:valueType>'."\n";
+        $xmp .= "\t\t\t\t\t\t\t\t".'</rdf:li>'."\n";
+        $xmp .= "\t\t\t\t\t\t\t".'</rdf:Seq>'."\n";
+        $xmp .= "\t\t\t\t\t\t".'</pdfaSchema:property>'."\n";
 		$xmp .= "\t\t\t\t\t".'</rdf:li>'."\n";
 		$xmp .= "\t\t\t\t\t".'<rdf:li rdf:parseType="Resource">'."\n";
 		$xmp .= "\t\t\t\t\t\t".'<pdfaSchema:namespaceURI>http://ns.adobe.com/xap/1.0/mm/</pdfaSchema:namespaceURI>'."\n";