diff --git a/rust/src/lib.rs b/rust/src/lib.rs
index 48b0bcef..ede4ebf1 100644
--- a/rust/src/lib.rs
+++ b/rust/src/lib.rs
@@ -72,6 +72,11 @@ mod ffi {
         fn script_is_ignored(pkg: &str, script: &str) -> bool;
     }
 
+    // testutils.rs
+    extern "Rust" {
+        fn testutils_entrypoint(argv: Vec<String>) -> Result<()>;
+    }
+
     /// Currently cxx-rs doesn't support mappings; like probably most projects,
     /// by far our most common case is a mapping from string -> string and since
     /// our data sizes aren't large, we serialize this as a vector of strings pairs.
@@ -158,7 +163,7 @@ pub use self::progress::*;
 mod scripts;
 pub(crate) use self::scripts::*;
 mod testutils;
-pub use self::testutils::*;
+pub(crate) use self::testutils::*;
 mod treefile;
 pub use self::treefile::*;
 mod utils;
diff --git a/rust/src/testutils.rs b/rust/src/testutils.rs
index 062a9527..554b6e3a 100644
--- a/rust/src/testutils.rs
+++ b/rust/src/testutils.rs
@@ -208,28 +208,10 @@ fn update_os_tree(opts: &SyntheticUpgradeOpts) -> Result<()> {
     Ok(())
 }
 
-fn testutils_main(args: &[String]) -> Result<()> {
+pub(crate) fn testutils_entrypoint(args: Vec<String>) -> Result<()> {
     let opt = Opt::from_iter(args.iter());
     match opt {
         Opt::GenerateSyntheticUpgrade(ref opts) => update_os_tree(opts)?,
     };
     Ok(())
 }
-
-mod ffi {
-    use super::*;
-    use glib_sys;
-    use libc;
-
-    use crate::ffiutil::*;
-
-    #[no_mangle]
-    pub extern "C" fn ror_testutils_entrypoint(
-        argv: *mut *mut libc::c_char,
-        gerror: *mut *mut glib_sys::GError,
-    ) -> libc::c_int {
-        let v: Vec<String> = unsafe { glib::translate::FromGlibPtrContainer::from_glib_none(argv) };
-        int_glib_error(testutils_main(&v), gerror)
-    }
-}
-pub use self::ffi::*;
diff --git a/src/app/rpmostree-builtin-testutils.cxx b/src/app/rpmostree-builtin-testutils.cxx
index 18f02e0f..1ac2a0ea 100644
--- a/src/app/rpmostree-builtin-testutils.cxx
+++ b/src/app/rpmostree-builtin-testutils.cxx
@@ -27,6 +27,7 @@
 #include "rpmostree-builtins.h"
 #include "rpmostree-rpm-util.h"
 #include "rpmostree-rust.h"
+#include "rpmostree-cxxrs.h"
 
 gboolean
 rpmostree_testutils_builtin_inject_pkglist (int argc, char **argv,
@@ -51,11 +52,11 @@ rpmostree_builtin_testutils (int argc, char **argv,
                                         invocation, cancellable, error);
   else
     {
-        g_autoptr(GPtrArray) args = g_ptr_array_new ();
-        for (int i = 0; i < argc; i++)
-          g_ptr_array_add (args, argv[i]);
-        g_ptr_array_add (args, NULL);
-        return ror_testutils_entrypoint ((char**)args->pdata, error);
+      rust::Vec<rust::String> rustargv;
+      for (int i = 0; i < argc; i++)
+        rustargv.push_back(std::string(argv[i]));
+      rpmostreecxx::testutils_entrypoint (rustargv);
+      return TRUE;
     }
 }