diff --git a/include/tug/Boundary.hpp b/include/tug/Boundary.hpp
index 3b900e3..2881d6a 100644
--- a/include/tug/Boundary.hpp
+++ b/include/tug/Boundary.hpp
@@ -211,4 +211,4 @@ private:
       boundaries; // Vector with Boundary Element information
 };
 
-#endif
+#endif // BOUNDARY_H_
diff --git a/include/tug/Grid.hpp b/include/tug/Grid.hpp
index 09ae737..d40e281 100644
--- a/include/tug/Grid.hpp
+++ b/include/tug/Grid.hpp
@@ -1,3 +1,6 @@
+#ifndef GRID_H_
+#define GRID_H_
+
 /**
  * @file Grid.hpp
  * @brief API of Grid class, that holds a matrix with concenctrations and a
@@ -174,3 +177,5 @@ private:
   MatrixXd alphaX;         // Matrix holding alpha coefficients in x-direction
   MatrixXd alphaY;         // Matrix holding alpha coefficients in y-direction
 };
+
+#endif // GRID_H_
diff --git a/include/tug/Simulation.hpp b/include/tug/Simulation.hpp
index f74ada6..60e87ac 100644
--- a/include/tug/Simulation.hpp
+++ b/include/tug/Simulation.hpp
@@ -5,8 +5,12 @@
  * options. Simulation object also holds a predefined Grid and Boundary object.
  *
  */
+
+#ifndef SIMULATION_H_
+#define SIMULATION_H_
+
 #include "Boundary.hpp"
-#include <ios>
+#include "Grid.hpp"
 
 using namespace std;
 
@@ -220,3 +224,5 @@ private:
   APPROACH approach;
   SOLVER solver;
 };
+
+#endif // SIMULATION_H_