diff --git a/devito/finite_differences/derivative.py b/devito/finite_differences/derivative.py
index c8d5f3d0da..cb94dfc388 100644
--- a/devito/finite_differences/derivative.py
+++ b/devito/finite_differences/derivative.py
@@ -445,7 +445,7 @@ def _eval_fd(self, expr, **kwargs):
         # Step 3: Evaluate FD of the new expression
         if self.method == 'RSFD':
             assert len(self.dims) == 1
-            assert self.deriv_order == 1
+            assert self.deriv_order[0] == 1
             res = d45(expr, self.dims[0], x0=self.x0, expand=expand)
         elif len(self.dims) > 1:
             assert self.method == 'FD'
diff --git a/tests/test_derivatives.py b/tests/test_derivatives.py
index 77c59ea390..da68343c77 100644
--- a/tests/test_derivatives.py
+++ b/tests/test_derivatives.py
@@ -87,18 +87,19 @@ def test_stencil_derivative(self, SymbolType, dim):
 
     @pytest.mark.parametrize('SymbolType, derivative, dim, expected', [
         (Function, ['dx2'], 3, 'Derivative(u(x, y, z), (x, 2))'),
-        (Function, ['dx2dy'], 3, 'Derivative(u(x, y, z), (x, 2), y)'),
-        (Function, ['dx2dydz'], 3, 'Derivative(u(x, y, z), (x, 2), y, z)'),
+        (Function, ['dx2dy'], 3, 'Derivative(Derivative(u(x, y, z), (x, 2)), y)'),
+        (Function, ['dx2dydz'], 3,
+         'Derivative(Derivative(Derivative(u(x, y, z), (x, 2)), y), z)'),
         (Function, ['dx2', 'dy'], 3, 'Derivative(Derivative(u(x, y, z), (x, 2)), y)'),
         (Function, ['dx2dy', 'dz2'], 3,
-         'Derivative(Derivative(u(x, y, z), (x, 2), y), (z, 2))'),
+         'Derivative(Derivative(Derivative(u(x, y, z), (x, 2)), y), (z, 2))'),
         (TimeFunction, ['dx2'], 3, 'Derivative(u(t, x, y, z), (x, 2))'),
-        (TimeFunction, ['dx2dy'], 3, 'Derivative(u(t, x, y, z), (x, 2), y)'),
+        (TimeFunction, ['dx2dy'], 3, 'Derivative(Derivative(u(t, x, y, z), (x, 2)), y)'),
         (TimeFunction, ['dx2', 'dy'], 3,
          'Derivative(Derivative(u(t, x, y, z), (x, 2)), y)'),
         (TimeFunction, ['dx', 'dy', 'dx2', 'dz', 'dydz'], 3,
-         'Derivative(Derivative(Derivative(Derivative(Derivative(u(t, x, y, z), x), y),' +
-         ' (x, 2)), z), y, z)')
+         'Derivative(Derivative(Derivative(Derivative(Derivative(Derivative(' +
+         'u(t, x, y, z), x), y), (x, 2)), z), y), z)')
     ])
     def test_unevaluation(self, SymbolType, derivative, dim, expected):
         u = SymbolType(name='u', grid=self.grid, time_order=2, space_order=2)