diff --git a/mounted_file_system.go b/mounted_file_system.go
index b1e52de..d456561 100644
--- a/mounted_file_system.go
+++ b/mounted_file_system.go
@@ -117,10 +117,25 @@ func (mfs *MountedFileSystem) mountAndServe(
 
 // Optional configuration accepted by Mount.
 type MountConfig struct {
+	// OS X only.
+	//
+	// Normally on OS X we mount with the novncache option
+	// (cf. http://goo.gl/1pTjuk), which disables entry caching in the kernel.
+	// This is because osxfuse does not support the entry expiration values we
+	// return to it (cf. http://goo.gl/8yR0Ie) and it is probably better to fail
+	// to cache than to cache for too long, since the latter is more likely to
+	// hide consistency bugs that are difficult to detect and diagnose.
+	//
+	// This field disables the use of novncache, restoring entry caching. Beware:
+	// the value of ChildInodeEntry.EntryExpiration is ignored by the kernel, and
+	// entries will be cached for an arbitrarily long time.
+	EnableVnodeCaching bool
 }
 
 // Convert to mount options to be passed to package bazilfuse.
 func (c *MountConfig) bazilfuseOptions() (opts []bazilfuse.MountOption) {
+	panic("TODO: Test and support MountConfig.EnableVnodeCaching")
+
 	opts = []bazilfuse.MountOption{
 		// Enable permissions checking in the kernel. See the comments on
 		// InodeAttributes.Mode.