diff --git a/compiler/builtins/bitcode/src/str.zig b/compiler/builtins/bitcode/src/str.zig
index 171b8ee910..938290f431 100644
--- a/compiler/builtins/bitcode/src/str.zig
+++ b/compiler/builtins/bitcode/src/str.zig
@@ -118,7 +118,7 @@ const RocStr = struct {
 // Str.split
 
 pub fn strSplitInPlace(
-    bytes_array: [*]u128,
+    array: [*]RocStr,
     array_len: usize,
     str_bytes_ptrs: [*]u8,
     str_len: usize,
@@ -126,8 +126,6 @@ pub fn strSplitInPlace(
     delimiter_len: usize
 ) callconv(.C) void {
 
-    var array = @ptrCast([*]RocStr, bytes_array);
-
     var ret_array_index : usize = 0;
 
     var sliceStart_index : usize = 0;
diff --git a/compiler/gen/src/llvm/build.rs b/compiler/gen/src/llvm/build.rs
index 6dbc9f64cf..bbf716d03e 100644
--- a/compiler/gen/src/llvm/build.rs
+++ b/compiler/gen/src/llvm/build.rs
@@ -550,11 +550,9 @@ pub fn build_exp_literal<'a, 'ctx, 'env>(
                     let len_type = env.ptr_int();
                     let len = len_type.const_int(bytes_len, false);
 
+                    // NOTE we rely on CHAR_LAYOUT turning into a `i8`
                     let ptr = allocate_list(env, InPlace::Clone, &CHAR_LAYOUT, len);
-                    let int_type = ptr_int(ctx, ptr_bytes);
-                    let ptr_as_int = builder.build_ptr_to_int(ptr, int_type, "list_cast_ptr");
                     let struct_type = collection(ctx, ptr_bytes);
-                    let len = BasicValueEnum::IntValue(env.ptr_int().const_int(len_u64, false));
 
                     let mut struct_val;
 
@@ -562,9 +560,9 @@ pub fn build_exp_literal<'a, 'ctx, 'env>(
                     struct_val = builder
                         .build_insert_value(
                             struct_type.get_undef(),
-                            ptr_as_int,
+                            ptr,
                             Builtin::WRAPPER_PTR,
-                            "insert_ptr",
+                            "insert_ptr_str_literal",
                         )
                         .unwrap();
 
@@ -1168,8 +1166,10 @@ fn list_literal<'a, 'ctx, 'env>(
     }
 
     let ptr_bytes = env.ptr_bytes;
-    let int_type = ptr_int(ctx, ptr_bytes);
-    let ptr_as_int = builder.build_ptr_to_int(ptr, int_type, "list_cast_ptr");
+
+    let u8_ptr_type = ctx.i8_type().ptr_type(AddressSpace::Generic);
+    let generic_ptr = cast_basic_basic(builder, ptr.into(), u8_ptr_type.into());
+
     let struct_type = collection(ctx, ptr_bytes);
     let len = BasicValueEnum::IntValue(env.ptr_int().const_int(len_u64, false));
     let mut struct_val;
@@ -1178,9 +1178,9 @@ fn list_literal<'a, 'ctx, 'env>(
     struct_val = builder
         .build_insert_value(
             struct_type.get_undef(),
-            ptr_as_int,
+            generic_ptr,
             Builtin::WRAPPER_PTR,
-            "insert_ptr",
+            "insert_ptr_list_literal",
         )
         .unwrap();
 
diff --git a/compiler/gen/src/llvm/build_list.rs b/compiler/gen/src/llvm/build_list.rs
index c024adda07..7335e91b35 100644
--- a/compiler/gen/src/llvm/build_list.rs
+++ b/compiler/gen/src/llvm/build_list.rs
@@ -1760,12 +1760,7 @@ pub fn load_list<'ctx>(
     wrapper_struct: StructValue<'ctx>,
     ptr_type: PointerType<'ctx>,
 ) -> (IntValue<'ctx>, PointerValue<'ctx>) {
-    let ptr_as_int = builder
-        .build_extract_value(wrapper_struct, Builtin::WRAPPER_PTR, "read_list_ptr")
-        .unwrap()
-        .into_int_value();
-
-    let ptr = builder.build_int_to_ptr(ptr_as_int, ptr_type, "list_cast_ptr");
+    let ptr = load_list_ptr(builder, wrapper_struct, ptr_type);
 
     let length = builder
         .build_extract_value(wrapper_struct, Builtin::WRAPPER_LEN, "list_len")
@@ -1780,12 +1775,14 @@ pub fn load_list_ptr<'ctx>(
     wrapper_struct: StructValue<'ctx>,
     ptr_type: PointerType<'ctx>,
 ) -> PointerValue<'ctx> {
-    let ptr_as_int = builder
+    // a `*mut u8` pointer
+    let generic_ptr = builder
         .build_extract_value(wrapper_struct, Builtin::WRAPPER_PTR, "read_list_ptr")
         .unwrap()
-        .into_int_value();
+        .into_pointer_value();
 
-    builder.build_int_to_ptr(ptr_as_int, ptr_type, "list_cast_ptr")
+    // cast to the expected pointer type
+    cast_basic_basic(builder, generic_ptr.into(), ptr_type.into()).into_pointer_value()
 }
 
 pub fn clone_nonempty_list<'a, 'ctx, 'env>(
@@ -1810,9 +1807,6 @@ pub fn clone_nonempty_list<'a, 'ctx, 'env>(
     // Allocate space for the new array that we'll copy into.
     let clone_ptr = allocate_list(env, inplace, elem_layout, list_len);
 
-    let int_type = ptr_int(ctx, ptr_bytes);
-    let ptr_as_int = builder.build_ptr_to_int(clone_ptr, int_type, "list_cast_ptr");
-
     // TODO check if malloc returned null; if so, runtime error for OOM!
 
     // Either memcpy or deep clone the array elements
@@ -1829,6 +1823,9 @@ pub fn clone_nonempty_list<'a, 'ctx, 'env>(
     }
 
     // Create a fresh wrapper struct for the newly populated array
+    let u8_ptr_type = ctx.i8_type().ptr_type(AddressSpace::Generic);
+    let generic_ptr = cast_basic_basic(builder, clone_ptr.into(), u8_ptr_type.into());
+
     let struct_type = collection(ctx, env.ptr_bytes);
     let mut struct_val;
 
@@ -1836,9 +1833,9 @@ pub fn clone_nonempty_list<'a, 'ctx, 'env>(
     struct_val = builder
         .build_insert_value(
             struct_type.get_undef(),
-            ptr_as_int,
+            generic_ptr,
             Builtin::WRAPPER_PTR,
-            "insert_ptr",
+            "insert_ptr_clone_nonempty_list",
         )
         .unwrap();
 
@@ -1915,26 +1912,28 @@ pub fn allocate_list<'a, 'ctx, 'env>(
 
 pub fn store_list<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
-    list_ptr: PointerValue<'ctx>,
+    pointer_to_first_element: PointerValue<'ctx>,
     len: IntValue<'ctx>,
 ) -> BasicValueEnum<'ctx> {
     let ctx = env.context;
     let builder = env.builder;
 
     let ptr_bytes = env.ptr_bytes;
-    let int_type = ptr_int(ctx, ptr_bytes);
-    let ptr_as_int = builder.build_ptr_to_int(list_ptr, int_type, "list_cast_ptr");
     let struct_type = collection(ctx, ptr_bytes);
 
+    let u8_ptr_type = ctx.i8_type().ptr_type(AddressSpace::Generic);
+    let generic_ptr =
+        cast_basic_basic(builder, pointer_to_first_element.into(), u8_ptr_type.into());
+
     let mut struct_val;
 
     // Store the pointer
     struct_val = builder
         .build_insert_value(
             struct_type.get_undef(),
-            ptr_as_int,
+            generic_ptr,
             Builtin::WRAPPER_PTR,
-            "insert_ptr",
+            "insert_ptr_store_list",
         )
         .unwrap();
 
diff --git a/compiler/gen/src/llvm/build_str.rs b/compiler/gen/src/llvm/build_str.rs
index 24092ed851..70fbc0fb53 100644
--- a/compiler/gen/src/llvm/build_str.rs
+++ b/compiler/gen/src/llvm/build_str.rs
@@ -60,17 +60,20 @@ pub fn str_split<'a, 'ctx, 'env>(
                     let ret_list_ptr =
                         allocate_list(env, inplace, &Layout::Builtin(Builtin::Str), segment_count);
 
-                    // convert `*mut RocStr` to `*mut i128`
-                    let ret_list_ptr_u128s = builder.build_bitcast(
+                    // get the RocStr type defined by zig
+                    let roc_str_type = env.module.get_struct_type("str.RocStr").unwrap();
+
+                    // convert `*mut { *mut u8, i64 }` to `*mut RocStr`
+                    let ret_list_ptr_zig_rocstr = builder.build_bitcast(
                         ret_list_ptr,
-                        ctx.i128_type().ptr_type(AddressSpace::Generic),
-                        "ret_u128_list",
+                        roc_str_type.ptr_type(AddressSpace::Generic),
+                        "convert_to_zig_rocstr",
                     );
 
                     call_void_bitcode_fn(
                         env,
                         &[
-                            ret_list_ptr_u128s,
+                            ret_list_ptr_zig_rocstr,
                             BasicValueEnum::IntValue(segment_count),
                             BasicValueEnum::PointerValue(str_bytes_ptr),
                             BasicValueEnum::IntValue(str_len),
@@ -533,7 +536,6 @@ fn clone_nonempty_str<'a, 'ctx, 'env>(
         Smallness::Big => {
             let clone_ptr = allocate_list(env, inplace, &CHAR_LAYOUT, len);
             let int_type = ptr_int(ctx, ptr_bytes);
-            let ptr_as_int = builder.build_ptr_to_int(clone_ptr, int_type, "list_cast_ptr");
 
             // TODO check if malloc returned null; if so, runtime error for OOM!
 
@@ -551,7 +553,7 @@ fn clone_nonempty_str<'a, 'ctx, 'env>(
             struct_val = builder
                 .build_insert_value(
                     struct_type.get_undef(),
-                    ptr_as_int,
+                    clone_ptr,
                     Builtin::WRAPPER_PTR,
                     "insert_ptr",
                 )
diff --git a/compiler/gen/src/llvm/convert.rs b/compiler/gen/src/llvm/convert.rs
index bd750e6067..cb7842b859 100644
--- a/compiler/gen/src/llvm/convert.rs
+++ b/compiler/gen/src/llvm/convert.rs
@@ -203,26 +203,13 @@ pub fn block_of_memory<'ctx>(
 
 /// Two usize values. Could be a wrapper for a List or a Str.
 ///
-/// It would be nicer if we could store this as a tuple containing one usize
-/// and one pointer. However, if we do that, we run into a problem with the
-/// empty list: it doesn't know what pointer type it should initailize to,
-/// so it can only create an empty (usize, usize) struct.
-///
-/// This way, we always initialize it to (usize, usize), and then if there's
-/// actually a pointer, we use build_int_to_ptr and build_ptr_to_int to convert
-/// the field when necessary. (It's not allowed to cast the entire struct from
-/// (usize, usize) to (usize, ptr) or vice versa.)
+/// This way, we always initialize it to (*mut u8, usize), and may have to cast the pointer type
+/// for lists.
 pub fn collection(ctx: &Context, ptr_bytes: u32) -> StructType<'_> {
-    let int_type = BasicTypeEnum::IntType(ptr_int(ctx, ptr_bytes));
+    let usize_type = ptr_int(ctx, ptr_bytes);
+    let u8_ptr = ctx.i8_type().ptr_type(AddressSpace::Generic);
 
-    ctx.struct_type(&[int_type, int_type], false)
-}
-
-/// Two usize values.
-pub fn collection_int_wrapper(ctx: &Context, ptr_bytes: u32) -> StructType<'_> {
-    let usize_type = BasicTypeEnum::IntType(ptr_int(ctx, ptr_bytes));
-
-    ctx.struct_type(&[usize_type, usize_type], false)
+    ctx.struct_type(&[u8_ptr.into(), usize_type.into()], false)
 }
 
 pub fn ptr_int(ctx: &Context, ptr_bytes: u32) -> IntType<'_> {
diff --git a/compiler/gen/src/llvm/refcounting.rs b/compiler/gen/src/llvm/refcounting.rs
index 2859c315f3..60e252e075 100644
--- a/compiler/gen/src/llvm/refcounting.rs
+++ b/compiler/gen/src/llvm/refcounting.rs
@@ -79,19 +79,13 @@ impl<'ctx> PointerToRefcount<'ctx> {
     }
 
     pub fn from_list_wrapper(env: &Env<'_, 'ctx, '_>, list_wrapper: StructValue<'ctx>) -> Self {
-        let ptr_as_int = env
+        let data_ptr = env
             .builder
             .build_extract_value(list_wrapper, Builtin::WRAPPER_PTR, "read_list_ptr")
             .unwrap()
-            .into_int_value();
+            .into_pointer_value();
 
-        let ptr = env.builder.build_int_to_ptr(
-            ptr_as_int,
-            env.context.i64_type().ptr_type(AddressSpace::Generic),
-            "list_int_to_ptr",
-        );
-
-        Self::from_ptr_to_data(env, ptr)
+        Self::from_ptr_to_data(env, data_ptr)
     }
 
     pub fn get_refcount<'a, 'env>(&self, env: &Env<'a, 'ctx, 'env>) -> IntValue<'ctx> {