diff --git a/src/openmc_regular_mesh_plotter/core.py b/src/openmc_regular_mesh_plotter/core.py
index 5f8e69f..7247e91 100644
--- a/src/openmc_regular_mesh_plotter/core.py
+++ b/src/openmc_regular_mesh_plotter/core.py
@@ -145,8 +145,8 @@ def plot_mesh_tally(
     default_imshow_kwargs.update(kwargs)
 
     if isinstance(tally, typing.Sequence):
-        data = np.zeros(shape=(40,40))
-        for one_tally in tally:
+        
+        for counter, one_tally in enumerate(tally):
             new_data = _get_tally_data(
                 scaling_factor,
                 mesh,
@@ -157,6 +157,8 @@ def plot_mesh_tally(
                 score,
                 slice_index
             )
+            if counter == 0:
+                data = np.zeros(shape=new_data.shape)
             data=data+new_data
     else:  # single tally
         data = _get_tally_data(
diff --git a/tests/test_units.py b/tests/test_units.py
index 92c730d..e4fceb1 100644
--- a/tests/test_units.py
+++ b/tests/test_units.py
@@ -151,12 +151,15 @@ def test_plot_two_mesh_tallies(model):
 
     mesh = openmc.RegularMesh().from_domain(geometry, dimension=[1, 20, 30])
     mesh_filter = openmc.MeshFilter(mesh)
+
     mesh_tally_1 = openmc.Tally(name="mesh-tal-1")
     mesh_tally_1.filters = [mesh_filter]
     mesh_tally_1.scores = ["flux"]
+
     mesh_tally_2 = openmc.Tally(name="mesh-tal-2")
     mesh_tally_2.filters = [mesh_filter]
     mesh_tally_2.scores = ["heating"]
+
     tallies = openmc.Tallies([mesh_tally_1, mesh_tally_2])
 
     model.tallies = tallies
@@ -179,7 +182,7 @@ def test_plot_two_mesh_tallies(model):
     plot.figure.savefig("t.png")
 
     plot = plot_mesh_tally(
-        tally=tally_result,
+        tally=[tally_result_1, tally_result_2],
         basis="yz",
         axis_units="m",
         # slice_index=9,  # max value of slice selected