diff --git a/src/skins/vector/css/molecules/voip/IncomingCallbox.css b/src/skins/vector/css/molecules/voip/IncomingCallbox.css
index 163ec43fcf..80e4920231 100644
--- a/src/skins/vector/css/molecules/voip/IncomingCallbox.css
+++ b/src/skins/vector/css/molecules/voip/IncomingCallbox.css
@@ -41,12 +41,14 @@ limitations under the License.
 
 .mx_IncomingCallBox_buttons {
     display: flex;
+    display: -webkit-flex;
 }
 
 .mx_IncomingCallBox_buttons_cell {
     vertical-align: middle;
     padding: 6px;
     flex: 1;
+    -webkit-flex: 1;
 }
 
 .mx_IncomingCallBox_buttons_decline,