diff --git a/UPGRADING.INTERNALS b/UPGRADING.INTERNALS
index 9b30458392a..22b9e6f660c 100644
--- a/UPGRADING.INTERNALS
+++ b/UPGRADING.INTERNALS
@@ -74,6 +74,7 @@ PHP 8.6 INTERNALS UPGRADE NOTES
   . _php_error_log() now has a formal return type of zend_result.
   . _php_error_log() now accepts zend_string* values instead of char*.
   . _php_error_log_ex() has been removed.
+  . php_mail()'s extra_cmd parameter is now a zend_string*.
 
 ========================
 4. OpCode changes
diff --git a/ext/mbstring/mbstring.c b/ext/mbstring/mbstring.c
index 12c366c33d5..c5331ef017a 100644
--- a/ext/mbstring/mbstring.c
+++ b/ext/mbstring/mbstring.c
@@ -4703,7 +4703,7 @@ PHP_FUNCTION(mb_send_mail)
 		extra_cmd = php_escape_shell_cmd(extra_cmd);
 	}
 
-	RETVAL_BOOL(php_mail(to_r, ZSTR_VAL(subject), message, ZSTR_VAL(str_headers), extra_cmd ? ZSTR_VAL(extra_cmd) : NULL));
+	RETVAL_BOOL(php_mail(to_r, ZSTR_VAL(subject), message, ZSTR_VAL(str_headers), extra_cmd));
 
 	if (extra_cmd) {
 		zend_string_release_ex(extra_cmd, 0);
diff --git a/ext/standard/mail.c b/ext/standard/mail.c
index 01e1148af08..395c7bb81d4 100644
--- a/ext/standard/mail.c
+++ b/ext/standard/mail.c
@@ -343,7 +343,7 @@ PHP_FUNCTION(mail)
 		extra_cmd = php_escape_shell_cmd(extra_cmd);
 	}
 
-	if (php_mail(to_r, subject_r, message, headers_str && ZSTR_LEN(headers_str) ? ZSTR_VAL(headers_str) : NULL, extra_cmd ? ZSTR_VAL(extra_cmd) : NULL)) {
+	if (php_mail(to_r, subject_r, message, headers_str && ZSTR_LEN(headers_str) ? ZSTR_VAL(headers_str) : NULL, extra_cmd)) {
 		RETVAL_TRUE;
 	} else {
 		RETVAL_FALSE;
@@ -434,7 +434,7 @@ static int php_mail_detect_multiple_crlf(const char *hdr) {
 
 
 /* {{{ php_mail */
-PHPAPI bool php_mail(const char *to, const char *subject, const char *message, const char *headers, const char *extra_cmd)
+PHPAPI bool php_mail(const char *to, const char *subject, const char *message, const char *headers, const zend_string *extra_cmd)
 {
 	FILE *sendmail;
 	char *sendmail_path = INI_STR("sendmail_path");
@@ -551,7 +551,7 @@ PHPAPI bool php_mail(const char *to, const char *subject, const char *message, c
 #endif
 	}
 	if (extra_cmd != NULL) {
-		spprintf(&sendmail_cmd, 0, "%s %s", sendmail_path, extra_cmd);
+		spprintf(&sendmail_cmd, 0, "%s %s", sendmail_path, ZSTR_VAL(extra_cmd));
 	} else {
 		sendmail_cmd = sendmail_path;
 	}
diff --git a/ext/standard/php_mail.h b/ext/standard/php_mail.h
index 731b70c0e10..bebb526699d 100644
--- a/ext/standard/php_mail.h
+++ b/ext/standard/php_mail.h
@@ -20,6 +20,6 @@
 PHP_MINFO_FUNCTION(mail);
 
 PHPAPI zend_string *php_mail_build_headers(const HashTable *headers);
-PHPAPI extern bool php_mail(const char *to, const char *subject, const char *message, const char *headers, const char *extra_cmd);
+PHPAPI extern bool php_mail(const char *to, const char *subject, const char *message, const char *headers, const zend_string *extra_cmd);
 
 #endif /* PHP_MAIL_H */