diff --git a/ProcessLib/Process.h b/ProcessLib/Process.h
index 720f31b77b06dd3258863a800a46c1a9098b1abf..8e48390979f624281242a26d57fcf42f12c7f4e9 100644
--- a/ProcessLib/Process.h
+++ b/ProcessLib/Process.h
@@ -79,8 +79,7 @@ public:
                               GlobalMatrix& Jac) override final;
 
     std::vector<NumLib::IndexValueVector<GlobalIndexType>> const*
-    getKnownSolutions(
-        double const t) const override final
+    getKnownSolutions(double const t) const override final
     {
         return _boundary_conditions.getKnownSolutions(t);
     }
@@ -103,6 +102,14 @@ public:
         return _secondary_variables;
     }
 
+    // used as call back for CalculateSurfaceFlux process
+    virtual std::vector<double> getFlux(std::size_t element_id,
+                                        MathLib::Point3d const& p,
+                                        GlobalVector const&) const
+    {
+        return std::vector<double>{};
+    }
+
 protected:
     NumLib::Extrapolator& getExtrapolator() const
     {