diff --git a/crates/sel4/sys/build/xml/invocations/mod.rs b/crates/sel4/sys/build/xml/invocations/mod.rs
index df1dd518f..91113f436 100644
--- a/crates/sel4/sys/build/xml/invocations/mod.rs
+++ b/crates/sel4/sys/build/xml/invocations/mod.rs
@@ -270,7 +270,7 @@ impl<'a> InvocationGenerator<'a> {
                             });
                         }
                         ParameterType::Bitfield => toks.extend(quote! {
-                            self.set_mr_bits(#start..#end, #name.0.inner()[0]);
+                            self.set_mr_bits_from_slice(#start..#end, #name.0.inner());
                         }),
                         ParameterType::Struct { members } => {
                             assert!(self.parameter_types.get(&param.ty).pass_by_reference());
diff --git a/crates/sel4/sys/src/ipc_buffer.rs b/crates/sel4/sys/src/ipc_buffer.rs
index 8e2eb69f1..3569cfc72 100644
--- a/crates/sel4/sys/src/ipc_buffer.rs
+++ b/crates/sel4/sys/src/ipc_buffer.rs
@@ -2,7 +2,7 @@ use core::mem;
 use core::ops::Range;
 use core::slice;
 
-use sel4_bitfield_ops::{get_bits, set_bits, PrimInt};
+use sel4_bitfield_ops::{get_bits, set_bits, set_bits_from_slice, PrimInt, UnsignedPrimInt};
 
 use crate::{seL4_CPtr, seL4_IPCBuffer, seL4_Word};
 
@@ -31,6 +31,14 @@ impl seL4_IPCBuffer {
         set_bits(&mut self.msg, range, T::cast_to_unsigned(value))
     }
 
+    pub(crate) fn set_mr_bits_from_slice<T>(&mut self, range: Range<usize>, value: &[T])
+    where
+        T: UnsignedPrimInt,
+        usize: TryFrom<T>,
+    {
+        set_bits_from_slice(&mut self.msg, range, value, 0)
+    }
+
     pub(crate) fn msg_bytes_mut(&mut self) -> &'static mut [u8] {
         let msg = &mut self.msg;
         unsafe {