diff --git a/guppylang/std/_internal/util.py b/guppylang/std/_internal/util.py
index 746423cb..5afe0f6e 100644
--- a/guppylang/std/_internal/util.py
+++ b/guppylang/std/_internal/util.py
@@ -80,11 +80,6 @@ def external_op(
     def op(ty: ht.FunctionType, inst: Inst) -> ops.DataflowOp:
         concrete_args = [make_concrete_arg(arg, inst, variable_remap) for arg in args]
         return op_def.instantiate(concrete_args, ty)
-        return ops.ExtOp(
-            op_def,
-            ty,
-            concrete_args,
-        )
 
     return op
 
diff --git a/guppylang/tys/builtin.py b/guppylang/tys/builtin.py
index 645266db..a022a3b4 100644
--- a/guppylang/tys/builtin.py
+++ b/guppylang/tys/builtin.py
@@ -136,9 +136,9 @@ def _array_to_hugr(args: Sequence[Argument]) -> ht.Type:
     # See `ArrayGetitemCompiler` for details.
     # Same also for classical arrays, see https://github.com/CQCL/guppylang/issues/629
     elem_ty = ht.Option(ty_arg.ty.to_hugr())
-
-    array = hugr.std.collections.array.EXTENSION.get_type("array")
-    return array.instantiate([len_arg.to_hugr(), ht.TypeTypeArg(elem_ty)])
+    hugr_arg = len_arg.to_hugr()
+    assert isinstance(hugr_arg, ht.BoundedNatArg)
+    return hugr.std.collections.array.Array(elem_ty, hugr_arg)
 
 
 def _sized_iter_to_hugr(args: Sequence[Argument]) -> ht.Type: