diff --git a/src/tool_cfgable.c b/src/tool_cfgable.c
index 7ad86cad3..64f15ca27 100644
--- a/src/tool_cfgable.c
+++ b/src/tool_cfgable.c
@@ -118,6 +118,7 @@ static void free_config_fields(struct OperationConfig *config)
 
   Curl_safefree(config->unix_socket_path);
   Curl_safefree(config->writeout);
+  Curl_safefree(config->proto_default);
 
   curl_slist_free_all(config->quote);
   curl_slist_free_all(config->postquote);