diff --git a/dune/fufem/assemblers/istlbackend.hh b/dune/fufem/assemblers/istlbackend.hh
index 2c7eb714f72dd9b6f15986f2c4a5d840ea4194e2..e84b285b8bad07500c04da1b738672dd3e8b9782 100644
--- a/dune/fufem/assemblers/istlbackend.hh
+++ b/dune/fufem/assemblers/istlbackend.hh
@@ -184,7 +184,7 @@ private:
   //! number of multi type cols (we assume the matrix is well-formed)
   static constexpr size_t colBlocks_ = Matrix::M();
   //! 2D array of IndexSets
-  std::array<std::array<Dune::MatrixIndexSet,rowBlocks_>,colBlocks_> indices_;
+  std::array<std::array<Dune::MatrixIndexSet,colBlocks_>,rowBlocks_> indices_;
   Matrix& matrix_;
 };