diff --git a/firedrake/assemble.py b/firedrake/assemble.py
index 875d27862e..f000643803 100644
--- a/firedrake/assemble.py
+++ b/firedrake/assemble.py
@@ -143,8 +143,8 @@ def get_assembler(form, *args, **kwargs):
 
     """
     is_base_form_preprocessed = kwargs.pop('is_base_form_preprocessed', False)
+    mat_type = kwargs.pop('mat_type', None)
     if isinstance(form, ufl.form.BaseForm) and not is_base_form_preprocessed:
-        mat_type = kwargs.get('mat_type', None)
         fc_params = kwargs.get('form_compiler_parameters', None)
         # Preprocess the DAG and restructure the DAG
         # Only pre-process `form` once beforehand to avoid pre-processing for each assembly call
@@ -156,7 +156,7 @@ def get_assembler(form, *args, **kwargs):
         elif len(form.arguments()) == 1 or diagonal:
             return OneFormAssembler(form, *args, diagonal=diagonal, **kwargs)
         elif len(form.arguments()) == 2:
-            return TwoFormAssembler(form, *args, **kwargs)
+            return TwoFormAssembler(form, *args, mat_type=mat_type, **kwargs)
         else:
             raise ValueError('Expecting a 0-, 1-, or 2-form: got %s' % (form))
     elif isinstance(form, ufl.core.expr.Expr) and not isinstance(form, ufl.core.base_form_operator.BaseFormOperator):