diff --git a/ext/curl/interface.c b/ext/curl/interface.c
index 9ab7a41201f0..426bd63093c9 100644
--- a/ext/curl/interface.c
+++ b/ext/curl/interface.c
@@ -1625,6 +1625,7 @@ static int curl_debug(CURL *cp, curl_infotype type, char *buf, size_t buf_len, v
 	if (type == CURLINFO_HEADER_OUT) {
 		if (ch->header.str) {
 			zend_string_release_ex(ch->header.str, 0);
+			ch->header.str = NULL;
 		}
 		if (buf_len > 0) {
 			ch->header.str = zend_string_init(buf, buf_len, 0);
@@ -3468,6 +3469,7 @@ static void curl_free_obj(zend_object *object)
 	zval_ptr_dtor(&ch->handlers.std_err);
 	if (ch->header.str) {
 		zend_string_release_ex(ch->header.str, 0);
+		ch->header.str = NULL;
 	}
 
 	zval_ptr_dtor(&ch->handlers.write_header->stream);