diff --git a/Tabs.php b/Tabs.php
index e671184..8872981 100644
--- a/Tabs.php
+++ b/Tabs.php
@@ -245,7 +245,7 @@ class Tabs extends Widget
                 continue;
             }
             if (!(array_key_exists('content', $item) xor array_key_exists('url', $item))) {
-                throw new InvalidConfigException("Either the 'content' or the 'url' option is required.");
+                throw new InvalidConfigException("Either the 'content' or the 'url' option is required, but only one can be set.");
             }
             if (array_key_exists('url', $item)) {
                 continue;