diff --git a/LibGit2Sharp/Core/GitWorktree.cs b/LibGit2Sharp/Core/GitWorktree.cs
index 64f90ebb7..c71cb16c0 100644
--- a/LibGit2Sharp/Core/GitWorktree.cs
+++ b/LibGit2Sharp/Core/GitWorktree.cs
@@ -33,8 +33,10 @@ internal enum GitWorktreePruneOptionFlags : uint
     internal class git_worktree_add_options
     {
         public uint version = 1;
-        
+
         public int locked;
+
+        public IntPtr @ref = IntPtr.Zero;
     }
 
     [StructLayout(LayoutKind.Sequential)]