diff --git a/dumux/discretization/box/fvgridgeometry.hh b/dumux/discretization/box/fvgridgeometry.hh
index 3aa0a3c70d04fddd9caa372c39fe6acdbca9d56c..cb40accda45d0890a9269a2e2f5e612548eea0a7 100644
--- a/dumux/discretization/box/fvgridgeometry.hh
+++ b/dumux/discretization/box/fvgridgeometry.hh
@@ -313,6 +313,10 @@ public:
     std::size_t periodicallyMappedDof(std::size_t dofIdx) const
     { return periodicVertexMap_.at(dofIdx); }
 
+    //! The index of the vertex / d.o.f. on the other side of the periodic boundary
+    const std::unordered_map<std::size_t, std::size_t> periodicVertexMap() const
+    { return periodicVertexMap_; }
+
 private:
 
     const FeCache feCache_;