diff --git a/openmc/mesh.py b/openmc/mesh.py
index af830158c..8ac4b1594 100644
--- a/openmc/mesh.py
+++ b/openmc/mesh.py
@@ -216,8 +216,8 @@ class StructuredMesh(MeshBase):
 
         Raises
         ------
-        RuntimeError
-            When the size of a dataset doesn't match the number of cells
+        ValueError
+            When the size of a dataset doesn't match the number of mesh cells
 
         Returns
         -------
@@ -229,14 +229,17 @@ class StructuredMesh(MeshBase):
         from vtk.util import numpy_support as nps
 
         # check that the data sets are appropriately sized
-        errmsg = "The size of the dataset {} should be equal to the number of cells"
         for label, dataset in datasets.items():
+            errmsg = (
+                f"The size of the dataset '{label}' ({dataset.size}) should be"
+                f" equal to the number of mesh cells ({self.num_mesh_cells})"
+            )
             if isinstance(dataset, np.ndarray):
-                if not dataset.size == self.dimension[0] * self.dimension[1]* self.dimension[2]:
-                    raise RuntimeError(errmsg.format(label))
+                if not dataset.size == self.num_mesh_cells:
+                    raise ValueError(errmsg)
             else:
-                if len(dataset) == self.dimension[0] * self.dimension[1]* self.dimension[2]:
-                    raise RuntimeError(errmsg.format(label))
+                if len(dataset) == self.num_mesh_cells:
+                    raise ValueError(errmsg)
             cv.check_type('label', label, str)
 
         vtk_grid = vtk.vtkStructuredGrid()
diff --git a/tests/unit_tests/test_mesh_to_vtk.py b/tests/unit_tests/test_mesh_to_vtk.py
index 26a393b41..d7d5907a2 100644
--- a/tests/unit_tests/test_mesh_to_vtk.py
+++ b/tests/unit_tests/test_mesh_to_vtk.py
@@ -28,6 +28,7 @@ spherical_mesh.r_grid = np.linspace(1, 2, num=30)
 spherical_mesh.phi_grid = np.linspace(0, np.pi, num=50)
 spherical_mesh.theta_grid = np.linspace(0, np.pi / 2, num=30)
 
+
 @pytest.mark.parametrize("mesh", [cylinder_mesh, regular_mesh, rectilinear_mesh, spherical_mesh])
 def test_write_data_to_vtk(mesh, tmpdir):
     # BUILD
@@ -43,7 +44,7 @@ def test_write_data_to_vtk(mesh, tmpdir):
 
     # read file
     reader = vtk.vtkStructuredGridReader()
-    reader.SetFileName(filename)
+    reader.SetFileName(str(filename))
     reader.Update()
 
     # check name of datasets
@@ -58,6 +59,7 @@ def test_write_data_to_vtk(mesh, tmpdir):
     assert nps.vtk_to_numpy(array1).size == data.size
     assert nps.vtk_to_numpy(array2).size == data.size
 
+
 @pytest.mark.parametrize("mesh", [cylinder_mesh, regular_mesh, rectilinear_mesh, spherical_mesh])
 def test_write_data_to_vtk_size_mismatch(mesh):
     """Checks that an error is raised when the size of the dataset
@@ -71,6 +73,12 @@ def test_write_data_to_vtk_size_mismatch(mesh):
     right_size = mesh.num_mesh_cells
     data = np.random.random(right_size + 1)
 
-    expected_error_msg = "The size of the dataset label should be equal to the number of cells"
-    with pytest.raises(RuntimeError, match=expected_error_msg):
-        mesh.write_data_to_vtk(filename="out.vtk", datasets={"label": data})
\ No newline at end of file
+    # Error message has \ in to escape characters that are otherwise recognized
+    # by regex. These are needed to make the test string match the error message
+    # string when using the match argument as that uses regular expression
+    expected_error_msg = (
+        f"The size of the dataset 'label' \({len(data)}\) should be equal to "
+        f"the number of mesh cells \({mesh.num_mesh_cells}\)"
+    )
+    with pytest.raises(ValueError, match=expected_error_msg):
+        mesh.write_data_to_vtk(filename="out.vtk", datasets={"label": data})