diff --git a/src/think/Validate.php b/src/think/Validate.php
index 0788406415..0b28152e3f 100644
--- a/src/think/Validate.php
+++ b/src/think/Validate.php
@@ -1146,7 +1146,7 @@ public function unique($value, $rule, array $data = [], string $field = ''): boo
                 }
             }
         } elseif (isset($data[$field])) {
-            $map[] = [$key, '=', $data[$field]];
+            $map[] = [$key ?: $field, '=', $data[$field]];
         } else {
             $map = [];
         }