diff --git a/errors.go b/errors.go
index 7ed27cb..860d7ec 100644
--- a/errors.go
+++ b/errors.go
@@ -3,12 +3,17 @@
 
 package fuse
 
-import bazilfuse "bazil.org/fuse"
+import (
+	"syscall"
+
+	bazilfuse "bazil.org/fuse"
+)
 
 const (
 	// Errors corresponding to kernel error numbers. These may be treated
 	// specially when returned by a FileSystem method.
-	ENOSYS = bazilfuse.ENOSYS
-	ENOENT = bazilfuse.ENOENT
-	EIO    = bazilfuse.EIO
+	EIO       = bazilfuse.EIO
+	ENOENT    = bazilfuse.ENOENT
+	ENOSYS    = bazilfuse.ENOSYS
+	ENOTEMPTY = bazilfuse.Errno(syscall.ENOTEMPTY)
 )
diff --git a/samples/memfs/fs.go b/samples/memfs/fs.go
index 6e8b216..31fe9f4 100644
--- a/samples/memfs/fs.go
+++ b/samples/memfs/fs.go
@@ -306,7 +306,22 @@ func (fs *memFS) RmDir(
 	parent := fs.getInodeForModifyingOrDie(req.Parent)
 	defer parent.mu.Unlock()
 
-	// TODO(jacobsa): Check for empty. (Make sure we have a failing test first.)
+	// Find the child within the parent.
+	childID, ok := parent.LookUpChild(req.Name)
+	if !ok {
+		err = fuse.ENOENT
+		return
+	}
+
+	// Grab the child.
+	child := fs.getInodeForModifyingOrDie(childID)
+	defer child.mu.Unlock()
+
+	// Make sure the child is empty.
+	if child.Len() != 0 {
+		err = fuse.ENOTEMPTY
+		return
+	}
 
 	// Remove the entry within the parent.
 	parent.RemoveChild(req.Name)
diff --git a/samples/memfs/inode.go b/samples/memfs/inode.go
index 2a3eb57..255dfe0 100644
--- a/samples/memfs/inode.go
+++ b/samples/memfs/inode.go
@@ -143,6 +143,20 @@ func (inode *inode) findChild(name string) (i int, ok bool) {
 // Public methods
 ////////////////////////////////////////////////////////////////////////
 
+// Return the number of children of the directory.
+//
+// REQUIRES: inode.dir
+// SHARED_LOCKS_REQUIRED(inode.mu)
+func (inode *inode) Len() (n int) {
+	for _, e := range inode.entries {
+		if e.Type != fuseutil.DT_Unknown {
+			n++
+		}
+	}
+
+	return
+}
+
 // Find an entry for the given child name and return its inode ID.
 //
 // REQUIRES: inode.dir
diff --git a/samples/memfs/memfs_test.go b/samples/memfs/memfs_test.go
index 01afb60..456681b 100644
--- a/samples/memfs/memfs_test.go
+++ b/samples/memfs/memfs_test.go
@@ -334,7 +334,7 @@ func (t *MemFSTest) Rmdir_NonEmpty() {
 	err = os.Remove(path.Join(t.mfs.Dir(), "foo"))
 
 	AssertNe(nil, err)
-	ExpectThat(err, Error(HasSubstr("non-empty")))
+	ExpectThat(err, Error(HasSubstr("not empty")))
 }
 
 func (t *MemFSTest) Rmdir_Empty() {