diff --git a/sys/fs/fdescfs/fdesc_vfsops.c b/sys/fs/fdescfs/fdesc_vfsops.c
index c175d0a3093..6356147b420 100644
--- a/sys/fs/fdescfs/fdesc_vfsops.c
+++ b/sys/fs/fdescfs/fdesc_vfsops.c
@@ -54,11 +54,21 @@
 
 static MALLOC_DEFINE(M_FDESCMNT, "fdesc_mount", "FDESC mount structure");
 
+static vfs_cmount_t	fdesc_cmount;
 static vfs_mount_t	fdesc_mount;
 static vfs_unmount_t	fdesc_unmount;
 static vfs_statfs_t	fdesc_statfs;
 static vfs_root_t	fdesc_root;
 
+/*
+ * Compatibility shim for old mount(2) system call.
+ */
+int
+fdesc_cmount(struct mntarg *ma, void *data, int flags, struct thread *td)
+{
+	return kernel_mount(ma, flags);
+}
+
 /*
  * Mount the per-process file descriptors (/dev/fd)
  */
@@ -193,6 +203,7 @@ fdesc_statfs(mp, sbp, td)
 }
 
 static struct vfsops fdesc_vfsops = {
+	.vfs_cmount =		fdesc_cmount,
 	.vfs_init =		fdesc_init,
 	.vfs_mount =		fdesc_mount,
 	.vfs_root =		fdesc_root,
diff --git a/sys/fs/pseudofs/pseudofs.c b/sys/fs/pseudofs/pseudofs.c
index 1fe0371711e..da1758b9303 100644
--- a/sys/fs/pseudofs/pseudofs.c
+++ b/sys/fs/pseudofs/pseudofs.c
@@ -284,6 +284,15 @@ pfs_mount(struct pfs_info *pi, struct mount *mp, struct thread *td)
 	return (0);
 }
 
+/*
+ * Compatibility shim for old mount(2) system call.
+ */
+int
+pfs_cmount(struct mntarg *ma, void *data, int flags, struct thread *td)
+{
+	return kernel_mount(ma, flags);
+}
+
 /*
  * Unmount a pseudofs instance
  */
diff --git a/sys/fs/pseudofs/pseudofs.h b/sys/fs/pseudofs/pseudofs.h
index 8eaa13735d3..b9701bc0933 100644
--- a/sys/fs/pseudofs/pseudofs.h
+++ b/sys/fs/pseudofs/pseudofs.h
@@ -34,6 +34,7 @@
 /*
  * Opaque structures
  */
+struct mntarg;
 struct mount;
 struct nameidata;
 struct proc;
@@ -199,6 +200,8 @@ struct pfs_node {
  */
 int		 pfs_mount	(struct pfs_info *pi, struct mount *mp,
 				 struct thread *td);
+int		 pfs_cmount	(struct mntarg *ma, void *data, int flags,
+				 struct thread *td);
 int		 pfs_unmount	(struct mount *mp, int mntflags,
 				 struct thread *td);
 int		 pfs_root	(struct mount *mp, int flags,
@@ -251,6 +254,7 @@ _##name##_uninit(struct vfsconf *vfc) {					\
 }									\
 									\
 static struct vfsops name##_vfsops = {					\
+	.vfs_cmount =		pfs_cmount,				\
 	.vfs_init =		_##name##_init,				\
 	.vfs_mount =		_##name##_mount,			\
 	.vfs_root =		pfs_root,				\
diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 1d1cc6cea73..2f609425886 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -736,9 +736,6 @@ mount(td, uap)
 	/* Kick out MNT_ROOTFS early as it is legal internally */
 	uap->flags &= ~MNT_ROOTFS;
 
-	if (uap->data == NULL)
-		return (EINVAL);
-
 	fstype = malloc(MFSNAMELEN, M_TEMP, M_WAITOK);
 	error = copyinstr(uap->type, fstype, MFSNAMELEN, NULL);
 	if (!error) {