diff --git a/www/common/onlyoffice/app-oo.less b/www/common/onlyoffice/app-oo.less
index 2971165a0..08b64df91 100644
--- a/www/common/onlyoffice/app-oo.less
+++ b/www/common/onlyoffice/app-oo.less
@@ -63,6 +63,9 @@ body.cp-app-sheet, body.cp-app-oodoc, body.cp-app-ooslide {
         display: flex;
         flex-flow: column;
         position: relative;
+        iframe {
+            flex: 1;
+        }
     }
     #cp-app-oo-offline {
         position: absolute;