diff --git a/lib/TemplateManager.php b/lib/TemplateManager.php
index 3e63c1d9c0..9d148127e8 100644
--- a/lib/TemplateManager.php
+++ b/lib/TemplateManager.php
@@ -478,7 +478,7 @@ public function formatNodeReturn(File $template) {
 			'preview' => $this->urlGenerator->linkToRouteAbsolute('richdocuments.templates.getPreview', ['fileId' => $template->getId()]),
 			'type' => $this->flipTypes()[$template->getMimeType()],
 			'delete' => $this->urlGenerator->linkToRouteAbsolute('richdocuments.templates.delete', ['fileId' => $template->getId()]),
-			'extension' => $template->getExtension(),
+			'extension' => ($ooxml && isset(self::TYPE_EXTENSION_OOXML[$documentType])) ? self::TYPE_EXTENSION_OOXML[$documentType] : self::TYPE_EXTENTION[$documentType],
 		];
 	}