diff --git a/Snakefile b/Snakefile
index c1fbb0e047d1f7f6b4ab376ed8df9cd1b9e217fc..1283a16dfedc356f75087e3158fc4d1e41aca7c0 100644
--- a/Snakefile
+++ b/Snakefile
@@ -30,8 +30,7 @@ TODO: Enforce Boxplot folds with decorator -> Done
 TODO: Enforce boundary for initial condition in exact solution only -> Done
 TODO: Adapt number of ghost cells based on ANN stencil -> Done
 TODO: Ensure exact solution is calculated in Equation class -> Done
-TODO: Extract objects from UpdateScheme
-TODO: Enforce num_ghost_cells to be positive integer for DG (not training)
+TODO: Enforce num_ghost_cells to be positive integer for DG -> Done
 TODO: Add Burger class
 TODO: Use cfl_number for updating, not just time (equation-related?)
 
@@ -56,6 +55,7 @@ TODO: Add verbose output
 TODO: Add tests for all functions
 
 Not feasible yet or doc-related:
+TODO: Extract objects from UpdateScheme
 TODO: Clean up result plotting (remove object properties of Equation)
 TODO: Add functions to create each object from dict
 TODO: Move plot_approximation_results() into plotting script
diff --git a/scripts/tcd/Equation.py b/scripts/tcd/Equation.py
index 995aba750f5ab282252d85a8bdb1abc7c4df19f8..e2765d25e7f1831dd68588c53f4fa2c3978adb80 100644
--- a/scripts/tcd/Equation.py
+++ b/scripts/tcd/Equation.py
@@ -53,6 +53,11 @@ class Equation(ABC):
         cfl_number : float
             CFL number to ensure stability.
 
+        Raises
+        ------
+        ValueError
+            If number of ghost cells in mesh in not positive.
+
         """
         self._quadrature = quadrature
         self._init_cond = init_cond
@@ -62,6 +67,10 @@ class Equation(ABC):
         self._wave_speed = wave_speed
         self._cfl_number = cfl_number
 
+        if self._mesh.num_ghost_cells <= 0:
+            raise ValueError('Number of ghost cells for calculations has to '
+                             'be positive.')
+
         self._reset()
 
     @property
diff --git a/scripts/tcd/Mesh.py b/scripts/tcd/Mesh.py
index 445ad170a3d3ee72e61b5f4d1529f2782fe1590a..abd4baa90b96f6eb34bc7e4f0d37f8836911a826 100644
--- a/scripts/tcd/Mesh.py
+++ b/scripts/tcd/Mesh.py
@@ -59,17 +59,22 @@ class Mesh:
             Right boundary of the mesh interval.
         num_ghost_cells : int, optional
             Number of ghost cells on each side of the mesh, respectively.
-            Default: False.
+            Default: 1.
 
         Raises
         ------
         ValueError
-            If number of cells is not exponential of 2.
+            If number of ghost cells is negative.
+        ValueError
+            If number of cells is not exponential of 2 (and ghost cells exist).
 
         """
         self._num_cells = num_cells
         self._num_ghost_cells = num_ghost_cells
         if self._num_ghost_cells != 0:
+            if self._num_ghost_cells < 0:
+                raise ValueError('The number of ghost cells has to be a '
+                                 'non-negative integer')
             if not math.log(self._num_cells, 2).is_integer():
                 raise ValueError('The number of cells in the mesh has to be '
                                  'an exponential of 2')