diff --git a/ProcessLib/Process.cpp b/ProcessLib/Process.cpp
index 98ed6566750c5a9f1d7583f0eb1beaf29e4d7053..9e9277e0169239101727d654193997de34c085e7 100644
--- a/ProcessLib/Process.cpp
+++ b/ProcessLib/Process.cpp
@@ -54,6 +54,7 @@ Process::Process(
     : name(std::move(name_)),
       _mesh(mesh),
       _secondary_variables(std::move(secondary_variables)),
+      cell_average_data_(mesh),
       _jacobian_assembler(std::move(jacobian_assembler)),
       _global_assembler(*_jacobian_assembler),
       _use_monolithic_scheme(use_monolithic_scheme),
diff --git a/ProcessLib/Process.h b/ProcessLib/Process.h
index 1816b836668da186e2062fa64c059408b627a3a9..be39d2bcb1369664303c9423abd2250578302833 100644
--- a/ProcessLib/Process.h
+++ b/ProcessLib/Process.h
@@ -21,6 +21,7 @@
 #include "ParameterLib/Parameter.h"
 #include "ProcessLib/BoundaryConditionAndSourceTerm/BoundaryConditionCollection.h"
 #include "ProcessLib/BoundaryConditionAndSourceTerm/SourceTermCollection.h"
+#include "ProcessLib/Output/CellAverageData.h"
 #include "ProcessLib/Output/ExtrapolatorData.h"
 #include "ProcessLib/Output/SecondaryVariable.h"
 #include "ProcessVariable.h"
@@ -361,6 +362,8 @@ protected:
 
     SecondaryVariableCollection _secondary_variables;
 
+    CellAverageData cell_average_data_;
+
     // TODO (CL) switch to the parallel vector matrix assembler here, once
     // feature complete, or use the assembly mixin and remove these two members.
     std::unique_ptr<ProcessLib::AbstractJacobianAssembler> _jacobian_assembler;