diff --git a/system/Database/Forge.php b/system/Database/Forge.php
index c95ced88c4d6..44373452465e 100644
--- a/system/Database/Forge.php
+++ b/system/Database/Forge.php
@@ -324,6 +324,7 @@ public function addKey($key, bool $primary = false, bool $unique = false)
             }
         } else {
             $this->keys[] = $key;
+            $this->keys   = array_unique($this->keys, SORT_REGULAR);
 
             if ($unique) {
                 $this->uniqueKeys[] = count($this->keys) - 1;