diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index d4f4cdae1..84ddd964b 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -1444,7 +1444,7 @@ void LocalStore::createUser(const std::string & userName, uid_t userId)
         createDirs(dir);
         if (chmod(dir.c_str(), 0755) == -1)
             throw SysError("changing permissions of directory '%s'", dir);
-        if (chown(dir.c_str(), userId, 0) == -1)
+        if (chown(dir.c_str(), userId, getgid()) == -1)
             throw SysError("changing owner of directory '%s'", dir);
     }
 }