diff --git a/firedrake/assemble.py b/firedrake/assemble.py
index 875d27862e..b838746b1d 100644
--- a/firedrake/assemble.py
+++ b/firedrake/assemble.py
@@ -1147,7 +1147,7 @@ class OneFormAssembler(ParloopFormAssembler):
 
     @classmethod
     def _cache_key(cls, form, bcs=None, form_compiler_parameters=None, needs_zeroing=True,
-                   zero_bc_nodes=True, diagonal=False, weight=1.0):
+                   zero_bc_nodes=True, diagonal=False, weight=1.0, **kwargs):
         bcs = solving._extract_bcs(bcs)
         return tuple(bcs), tuplify(form_compiler_parameters), needs_zeroing, zero_bc_nodes, diagonal, weight