diff --git a/webv4/components/twit-button.xjs b/webv4/components/twit-button.xjs
index 94af80f7dbb662cf70d88451b7588163fe536a2a..7ed724db8d4b7330b715e64092b76c8bdc74fb76 100644
--- a/webv4/components/twit-button.xjs
+++ b/webv4/components/twit-button.xjs
@@ -1,4 +1,4 @@
 <? var _bs = locale.get('button_block_sender', 'page_forum'); ?>
-<button id="bsb-%s" class="btn btn-default icon" aria-label="<? write(_bs); ?>" title="<? write(_bs); ?>" onclick="blockSender('%s', '%s', '%s')">
+<button id="bsb-%s" class="btn btn-default icon" aria-label="<? write(_bs); ?>" title="<? write(_bs); ?>" onclick="var result = confirm('Permanently block this sender?'); if (result) { blockSender('%s', '%s', '%s') }">
     <span class="glyphicon glyphicon-ban-circle"></span>
 </button>
\ No newline at end of file