diff --git a/ProcessLib/ThermoRichardsMechanics/ThermoRichardsMechanicsProcess.cpp b/ProcessLib/ThermoRichardsMechanics/ThermoRichardsMechanicsProcess.cpp
index acdf602bfa9b85cb998d37d48c10c6a5a70587b4..c4204f086ac487268d7cbefd04fa68743a8dfefa 100644
--- a/ProcessLib/ThermoRichardsMechanics/ThermoRichardsMechanicsProcess.cpp
+++ b/ProcessLib/ThermoRichardsMechanics/ThermoRichardsMechanicsProcess.cpp
@@ -44,6 +44,9 @@ ThermoRichardsMechanicsProcess<DisplacementDim, ConstitutiveTraits>::
     : Process(std::move(name), mesh, std::move(jacobian_assembler), parameters,
               integration_order, std::move(process_variables),
               std::move(secondary_variables), use_monolithic_scheme),
+      AssemblyMixin<
+          ThermoRichardsMechanicsProcess<DisplacementDim, ConstitutiveTraits>>{
+          *_jacobian_assembler},
       process_data_(std::move(process_data))
 {
     ProcessLib::Reflection::addReflectedIntegrationPointWriters<