diff --git a/src/amdis/common/Transposed.hpp b/src/amdis/common/Transposed.hpp
index 38920b9665f73ce240b180505a604bb68bc63f1b..f99011ce7af75f44cbec31b2ea056624a9f97938 100644
--- a/src/amdis/common/Transposed.hpp
+++ b/src/amdis/common/Transposed.hpp
@@ -65,6 +65,18 @@ namespace AMDiS
       return matrix_.N();
     }
 
+    template <class Mat>
+    TransposedMatrix& operator+=(Mat const& mat)
+    {
+      assert(mat.N() == N());
+      assert(mat.M() == M());
+      for (size_type i = 0; i < N(); ++i)
+        for (size_type j = 0; j < M(); ++j)
+          (*this)[i][j] += mat[i][j];
+
+      return *this;
+    }
+
   private:
     Matrix& matrix_;
   };