diff --git a/nac3artiq/src/codegen.rs b/nac3artiq/src/codegen.rs
index 489115d1..9db031d2 100644
--- a/nac3artiq/src/codegen.rs
+++ b/nac3artiq/src/codegen.rs
@@ -29,7 +29,10 @@ use pyo3::{
 
 use crate::{symbol_resolver::InnerResolver, timeline::TimeFns};
 
+use inkwell::types::BasicType;
 use itertools::Itertools;
+use nac3core::codegen::classes::{ArrayLikeIndexer, ArrayLikeValue, NDArrayType};
+use nac3core::codegen::llvm_intrinsics;
 use std::{
     collections::{hash_map::DefaultHasher, HashMap},
     hash::{Hash, Hasher},
@@ -444,10 +447,11 @@ fn rpc_codegen_callback_fn<'ctx>(
     args: Vec<(Option<StrRef>, ValueEnum<'ctx>)>,
     generator: &mut dyn CodeGenerator,
 ) -> Result<Option<BasicValueEnum<'ctx>>, String> {
-    let ptr_type = ctx.ctx.i8_type().ptr_type(AddressSpace::default());
-    let size_type = generator.get_size_type(ctx.ctx);
+    let int1 = ctx.ctx.bool_type();
     let int8 = ctx.ctx.i8_type();
     let int32 = ctx.ctx.i32_type();
+    let size_type = generator.get_size_type(ctx.ctx);
+    let ptr_type = int8.ptr_type(AddressSpace::default());
     let tag_ptr_type = ctx.ctx.struct_type(&[ptr_type.into(), size_type.into()], false);
 
     let service_id = int32.const_int(fun.1 .0 as u64, false);
@@ -541,26 +545,56 @@ fn rpc_codegen_callback_fn<'ctx>(
         let arg_slot =
             generator.gen_var_alloc(ctx, arg.get_type(), Some(&format!("rpc.arg{i}"))).unwrap();
         ctx.builder.build_store(arg_slot, *arg).unwrap();
-        let arg_slot = ctx
-            .builder
-            .build_bitcast(arg_slot, ptr_type, "rpc.arg")
-            .map(BasicValueEnum::into_pointer_value)
-            .unwrap();
         let arg_slot = if matches!(&*ctx.unifier.get_ty_immutable(*arg_ty), TypeEnum::TObj { obj_id, .. } if *obj_id == PrimDef::NDArray.id())
         {
-            debug_assert_eq!(u64::from(size_type.get_bit_width() / 8), 4);
+            let (elem_ty, _) = unpack_ndarray_var_tys(&mut ctx.unifier, *arg_ty);
+            let llvm_arg_ty =
+                NDArrayType::new(generator, ctx.ctx, ctx.get_llvm_type(generator, elem_ty));
+            let llvm_arg = NDArrayValue::from_ptr_val(arg.into_pointer_value(), size_type, None);
 
-            unsafe {
-                ctx.builder
-                    .build_in_bounds_gep(
-                        arg_slot,
-                        &[size_type.const_int(4, false)], // should be 4
-                        "",
-                    )
-                    .unwrap()
-            }
+            let llvm_usize_sizeof = llvm_arg_ty.size_type().size_of();
+            let llvm_elem_sizeof = llvm_arg_ty.element_type().size_of().unwrap();
+
+            let dims_buf_sz =
+                ctx.builder.build_int_mul(llvm_arg.load_ndims(ctx), llvm_usize_sizeof, "").unwrap();
+            let data_buf_sz = ctx
+                .builder
+                .build_int_mul(
+                    call_ndarray_calc_size(generator, ctx, &llvm_arg.dim_sizes(), (None, None)),
+                    llvm_elem_sizeof,
+                    "",
+                )
+                .unwrap();
+
+            let buffer_size = ctx.builder.build_int_add(dims_buf_sz, data_buf_sz, "").unwrap();
+
+            let buffer =
+                generator.gen_array_var_alloc(ctx, int8.into(), buffer_size, None).unwrap();
+
+            llvm_intrinsics::call_memcpy_generic(
+                ctx,
+                buffer.base_ptr(ctx, generator),
+                llvm_arg.dim_sizes().base_ptr(ctx, generator),
+                dims_buf_sz,
+                int1.const_zero(),
+            );
+
+            let pbuffer_data_begin =
+                unsafe { buffer.ptr_offset_unchecked(ctx, generator, &dims_buf_sz, None) };
+            llvm_intrinsics::call_memcpy_generic(
+                ctx,
+                pbuffer_data_begin,
+                llvm_arg.data().base_ptr(ctx, generator),
+                data_buf_sz,
+                int1.const_zero(),
+            );
+
+            buffer.base_ptr(ctx, generator)
         } else {
-            arg_slot
+            ctx.builder
+                .build_bitcast(arg_slot, ptr_type, "rpc.arg")
+                .map(BasicValueEnum::into_pointer_value)
+                .unwrap()
         };
         let arg_ptr = unsafe {
             ctx.builder.build_gep(