diff --git a/libfuse/include/fuse_cfg.hpp b/libfuse/include/fuse_cfg.hpp
index 6ac24347..09cf4b70 100644
--- a/libfuse/include/fuse_cfg.hpp
+++ b/libfuse/include/fuse_cfg.hpp
@@ -10,6 +10,7 @@ struct fuse_cfg_t
   bool valid_uid() const;
 
   s64 gid = -1;
+  bool valid_gid() const;
 
   s64 remember = 0;