diff --git a/dune/fufem/prolongboundarypatch.hh b/dune/fufem/prolongboundarypatch.hh
index 6b027ef3e02d3aa8ba31e3557fd77ea18c330be0..b0e14eaa1c44b4428305e1b3b03587ae6e212d29 100644
--- a/dune/fufem/prolongboundarypatch.hh
+++ b/dune/fufem/prolongboundarypatch.hh
@@ -55,7 +55,7 @@ public:
                     const int dim      = GridType::dimension;
                     const int dimworld = GridType::dimensionworld;
                     typedef typename GridType::ctype ctype;
-                    FieldVector<ctype,dimworld-1> dummy;
+                    FieldVector<ctype,dim-1> dummy;
                     FieldVector<ctype,dimworld> level0Normal = i.unitOuterNormal(dummy);
 
                     // Find all boundary segments of the descendants of this element