diff --git a/nac3core/src/codegen/model/ptr.rs b/nac3core/src/codegen/model/ptr.rs
index baff1497..5574aad8 100644
--- a/nac3core/src/codegen/model/ptr.rs
+++ b/nac3core/src/codegen/model/ptr.rs
@@ -123,9 +123,9 @@ impl<'ctx, Item: Model<'ctx>> Instance<'ctx, Ptr<Item>> {
     pub fn offset_const(
         &self,
         ctx: &CodeGenContext<'ctx, '_>,
-        offset: u64,
+        offset: i64,
     ) -> Instance<'ctx, Ptr<Item>> {
-        let offset = ctx.ctx.i32_type().const_int(offset, false);
+        let offset = ctx.ctx.i64_type().const_int(offset as u64, true);
         self.offset(ctx, offset)
     }
 
@@ -141,7 +141,7 @@ impl<'ctx, Item: Model<'ctx>> Instance<'ctx, Ptr<Item>> {
     pub fn set_index_const(
         &self,
         ctx: &CodeGenContext<'ctx, '_>,
-        index: u64,
+        index: i64,
         value: Instance<'ctx, Item>,
     ) {
         self.offset_const(ctx, index).store(ctx, value);
@@ -160,7 +160,7 @@ impl<'ctx, Item: Model<'ctx>> Instance<'ctx, Ptr<Item>> {
         &self,
         generator: &mut G,
         ctx: &CodeGenContext<'ctx, '_>,
-        index: u64,
+        index: i64,
     ) -> Instance<'ctx, Item> {
         self.offset_const(ctx, index).load(generator, ctx)
     }