diff --git a/arraycontext/container/arithmetic.py b/arraycontext/container/arithmetic.py
index 2ef5ddc91dace71497598575c747860c790c7063..4c8a09a6ad611458f7c5299fb75219ac1eb243cd 100644
--- a/arraycontext/container/arithmetic.py
+++ b/arraycontext/container/arithmetic.py
@@ -214,6 +214,15 @@ def with_container_arithmetic(
     if rel_comparison is None:
         raise TypeError("rel_comparison must be specified")
 
+    if bcast_numpy_array:
+        from warnings import warn
+        warn("'bcast_numpy_array=True' is deprecated and will be unsupported"
+             " from December 2021", DeprecationWarning, stacklevel=2)
+
+        if _bcast_actx_array_type:
+            raise ValueError("'bcast_numpy_array' and '_bcast_actx_array_type'"
+                             " cannot be both set.")
+
     if rel_comparison and eq_comparison is None:
         eq_comparison = True