diff --git a/src/Instagram/Auth/Checkpoint/ImapClient.php b/src/Instagram/Auth/Checkpoint/ImapClient.php
index 8b7caf5..669ab27 100644
--- a/src/Instagram/Auth/Checkpoint/ImapClient.php
+++ b/src/Instagram/Auth/Checkpoint/ImapClient.php
@@ -136,7 +136,7 @@ public function getLastInstagramEmailContent(int $try = 1): string
                 }
 
                 if ($isMailFromInstagram && isset($match[1])) {
-                    imap_delete($resource, $i);
+                    imap_delete($resource, "$i");
 
                     $foundCode = true;
                     $code      = $match[1];