diff --git a/stdlib/2and3/imaplib.pyi b/stdlib/2and3/imaplib.pyi
index ecf80c0ff..ab32e7bac 100644
--- a/stdlib/2and3/imaplib.pyi
+++ b/stdlib/2and3/imaplib.pyi
@@ -69,7 +69,7 @@ class IMAP4:
     def partial(self, message_num: str, message_part: str, start: str, length: str) -> CommandResults: ...
     def proxyauth(self, user: str) -> CommandResults: ...
     def rename(self, oldmailbox: str, newmailbox: str) -> CommandResults: ...
-    def search(self, charset: str, *criteria: str) -> CommandResults: ...
+    def search(self, charset: Optional[str], *criteria: str) -> CommandResults: ...
     def select(self, mailbox: str = ..., readonly: bool = ...) -> CommandResults: ...
     def setacl(self, mailbox: str, who: str, what: str) -> CommandResults: ...
     def setannotation(self, *args: List[str]) -> CommandResults: ...