diff --git a/library/think/model/Merge.php b/library/think/model/Merge.php
index 1bf634f4..9a28ea9c 100644
--- a/library/think/model/Merge.php
+++ b/library/think/model/Merge.php
@@ -189,8 +189,12 @@ class Merge extends Model
 
                 if (!empty($where)) {
                     $pk = $this->getPk();
-                    if (is_string($pk) && isset($data[$pk])) {
-                        unset($data[$pk]);
+
+                    if (isset($this->mapFields[$pk])) {
+                        $pk = $this->mapFields[$pk];
+                    }
+                    if (isset($where[$pk])) {
+                        unset($where[$pk]);
                     }
                 }