diff --git a/nac3core/src/codegen/irrt/mod.rs b/nac3core/src/codegen/irrt/mod.rs
index 8459129a1..923ae9c61 100644
--- a/nac3core/src/codegen/irrt/mod.rs
+++ b/nac3core/src/codegen/irrt/mod.rs
@@ -329,10 +329,36 @@ pub fn list_slice_assignment<'ctx, 'a>(
     // index in bound and positive should be done
     // assert if dest.step == 1 then len(src) <= len(dest) else len(src) == len(dest), and
     // throw exception if not satisfied
+    let src_end = ctx.builder
+        .build_select(
+            ctx.builder.build_int_compare(
+                inkwell::IntPredicate::SLT,
+                src_idx.2,
+                zero,
+                "is_neg",
+            ),
+            ctx.builder.build_int_sub(src_idx.1, one, "e_min_one"),
+            ctx.builder.build_int_add(src_idx.1, one, "e_add_one"),
+            "final_e",
+        )
+        .into_int_value();
+    let dest_end = ctx.builder
+        .build_select(
+            ctx.builder.build_int_compare(
+                inkwell::IntPredicate::SLT,
+                dest_idx.2,
+                zero,
+                "is_neg",
+            ),
+            ctx.builder.build_int_sub(dest_idx.1, one, "e_min_one"),
+            ctx.builder.build_int_add(dest_idx.1, one, "e_add_one"),
+            "final_e",
+        )
+        .into_int_value();
     let src_slice_len =
-        calculate_len_for_slice_range(generator, ctx, src_idx.0, src_idx.1, src_idx.2);
+        calculate_len_for_slice_range(generator, ctx, src_idx.0, src_end, src_idx.2);
     let dest_slice_len =
-        calculate_len_for_slice_range(generator, ctx, dest_idx.0, dest_idx.1, dest_idx.2);
+        calculate_len_for_slice_range(generator, ctx, dest_idx.0, dest_end, dest_idx.2);
     let src_eq_dest = ctx.builder.build_int_compare(
         IntPredicate::EQ,
         src_slice_len,
@@ -357,7 +383,7 @@ pub fn list_slice_assignment<'ctx, 'a>(
         generator,
         cond,
         "0:ValueError",
-        "attempt to assign sequence of size {0}, to slice of size {1} with step size {2}",
+        "attempt to assign sequence of size {0} to slice of size {1} with step size {2}",
         [Some(src_slice_len), Some(dest_slice_len), Some(dest_idx.2)],
         ctx.current_loc,
     );