diff --git a/src/main/java/org/olat/core/util/openxml/OpenXMLUtils.java b/src/main/java/org/olat/core/util/openxml/OpenXMLUtils.java
index 87e2edbbf0f517e7442b26125be01d301b87d2b3..307ece7f899431913d18b8d9e5599057db2d7404 100644
--- a/src/main/java/org/olat/core/util/openxml/OpenXMLUtils.java
+++ b/src/main/java/org/olat/core/util/openxml/OpenXMLUtils.java
@@ -132,7 +132,7 @@ public class OpenXMLUtils {
 	
 	public static final XMLStreamWriter createStreamWriter(ZipOutputStream out) {
 		try {
-			return XMLOutputFactory.newInstance().createXMLStreamWriter(new ShieldOutputStream(out));
+			return XMLOutputFactory.newInstance().createXMLStreamWriter(new ShieldOutputStream(out), "UTF-8");
 		} catch (XMLStreamException | FactoryConfigurationError e) {
 			log.error("", e);
 			return null;