diff --git a/compiler/gen_llvm/src/llvm/convert.rs b/compiler/gen_llvm/src/llvm/convert.rs
index 3b37bfa000..5f97a18f24 100644
--- a/compiler/gen_llvm/src/llvm/convert.rs
+++ b/compiler/gen_llvm/src/llvm/convert.rs
@@ -132,6 +132,15 @@ pub fn argument_type_from_layout<'a, 'ctx, 'env>(
             argument_type_from_layout(env, &lambda_set.runtime_representation())
         }
         Union(union_layout) => argument_type_from_union_layout(env, union_layout),
+        Builtin(_) => {
+            let base = basic_type_from_layout(env, layout);
+
+            if layout.is_passed_by_reference() {
+                base.ptr_type(AddressSpace::Generic).into()
+            } else {
+                base
+            }
+        }
         other => basic_type_from_layout(env, other),
     }
 }
diff --git a/compiler/gen_llvm/src/llvm/refcounting.rs b/compiler/gen_llvm/src/llvm/refcounting.rs
index 1bd968c118..0098432aa5 100644
--- a/compiler/gen_llvm/src/llvm/refcounting.rs
+++ b/compiler/gen_llvm/src/llvm/refcounting.rs
@@ -20,7 +20,7 @@ use roc_module::symbol::Symbol;
 use roc_mono::layout::{Builtin, Layout, LayoutIds, UnionLayout};
 use roc_target::TargetInfo;
 
-use super::convert::argument_type_from_union_layout;
+use super::convert::{argument_type_from_layout, argument_type_from_union_layout};
 
 /// "Infinite" reference count, for static values
 /// Ref counts are encoded as negative numbers where isize::MIN represents 1
@@ -687,7 +687,7 @@ fn modify_refcount_list<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let basic_type = basic_type_from_layout(env, layout);
+            let basic_type = argument_type_from_layout(env, layout);
             let function_value = build_header(env, basic_type, mode, &fn_name);
 
             modify_refcount_list_help(
@@ -824,7 +824,7 @@ fn modify_refcount_str<'a, 'ctx, 'env>(
     let function = match env.module.get_function(fn_name.as_str()) {
         Some(function_value) => function_value,
         None => {
-            let basic_type = basic_type_from_layout(env, layout);
+            let basic_type = argument_type_from_layout(env, layout);
             let function_value = build_header(env, basic_type, mode, &fn_name);
 
             modify_refcount_str_help(env, mode, layout, function_value);