diff --git a/lib/blocklib.php b/lib/blocklib.php
index 6787a37edf6..0aa7f80c32c 100644
--- a/lib/blocklib.php
+++ b/lib/blocklib.php
@@ -880,7 +880,7 @@ class block_manager {
 
         confirm_sesskey();
 
-        if ($this->page->user_can_edit_blocks()) {
+        if (!$this->page->user_can_edit_blocks()) {
             throw new moodle_exception('nopermissions', '', $this->page->url->out(), get_string('addblock'));
         }