diff --git a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
index 3099cf9f31..e8a221b814 100644
--- a/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
+++ b/src/gt4py/next/iterator/transforms/fuse_as_fieldop.py
@@ -53,7 +53,7 @@ def _canonicalize_as_fieldop(expr: itir.FunCall) -> itir.FunCall:
     if cpm.is_ref_to(stencil, "deref"):
         stencil = im.lambda_("arg")(im.deref("arg"))
         new_expr = im.as_fieldop(stencil, domain)(*expr.args)
-        type_inference.copy_type(from_=expr, to=new_expr)
+        type_inference.copy_type(from_=expr, to=new_expr, allow_untyped=True)
 
         return new_expr
 
@@ -164,7 +164,7 @@ def fuse_as_fieldop(
     )
     new_node = inline_lifts.InlineLifts().visit(new_node)
 
-    type_inference.copy_type(from_=expr, to=new_node)
+    type_inference.copy_type(from_=expr, to=new_node, allow_untyped=True)
 
     return new_node