diff --git a/rust/src/composepost.rs b/rust/src/composepost.rs
index 481072c8..ccb58a5a 100644
--- a/rust/src/composepost.rs
+++ b/rust/src/composepost.rs
@@ -84,29 +84,12 @@ fn postprocess_subs_dist(rootfs_dfd: &openat::Dir) -> Result<()> {
 
 // This function is called from rpmostree_postprocess_final(); think of
 // it as the bits of that function that we've chosen to implement in Rust.
-fn compose_postprocess_final(rootfs_dfd: &openat::Dir) -> Result<()> {
+pub(crate) fn compose_postprocess_final(rootfs_dfd: i32) -> Result<()> {
+    let rootfs_dfd = crate::ffiutil::ffi_view_openat_dir(rootfs_dfd);
     let tasks = [
         postprocess_useradd,
         postprocess_presets,
         postprocess_subs_dist,
     ];
-    tasks.par_iter().try_for_each(|f| f(rootfs_dfd))
+    tasks.par_iter().try_for_each(|f| f(&rootfs_dfd))
 }
-
-mod ffi {
-    use super::*;
-    use glib_sys;
-    use libc;
-
-    use crate::ffiutil::*;
-
-    #[no_mangle]
-    pub extern "C" fn ror_compose_postprocess_final(
-        rootfs_dfd: libc::c_int,
-        gerror: *mut *mut glib_sys::GError,
-    ) -> libc::c_int {
-        let rootfs_dfd = ffi_view_openat_dir(rootfs_dfd);
-        int_glib_error(compose_postprocess_final(&rootfs_dfd), gerror)
-    }
-}
-pub use self::ffi::*;
diff --git a/rust/src/lib.rs b/rust/src/lib.rs
index 32ead3da..1ffeebce 100644
--- a/rust/src/lib.rs
+++ b/rust/src/lib.rs
@@ -48,6 +48,11 @@ mod ffi {
         fn get_systemctl_wrapper() -> &'static [u8];
     }
 
+    // composepost.rs
+    extern "Rust" {
+        fn compose_postprocess_final(rootfs_dfd: i32) -> Result<()>;
+    }
+
     // initramfs.rs
     extern "Rust" {
         fn get_dracut_random_cpio() -> &'static [u8];
@@ -105,7 +110,7 @@ pub(crate) use client::*;
 mod cliwrap;
 pub use cliwrap::*;
 mod composepost;
-pub use self::composepost::*;
+pub(crate) use composepost::*;
 mod core;
 use crate::core::*;
 mod history;
diff --git a/src/libpriv/rpmostree-postprocess.cxx b/src/libpriv/rpmostree-postprocess.cxx
index 68a5b773..38e50129 100644
--- a/src/libpriv/rpmostree-postprocess.cxx
+++ b/src/libpriv/rpmostree-postprocess.cxx
@@ -984,8 +984,7 @@ rpmostree_postprocess_final (int            rootfs_dfd,
                                                                error))
     return FALSE;
 
-  if (!ror_compose_postprocess_final (rootfs_dfd, error))
-    return FALSE;
+  rpmostreecxx::compose_postprocess_final (rootfs_dfd);
 
   if (selinux)
     {