diff --git a/openmc/mgxs/mgxs.py b/openmc/mgxs/mgxs.py
index e9ce00254d..968504a06d 100644
--- a/openmc/mgxs/mgxs.py
+++ b/openmc/mgxs/mgxs.py
@@ -789,10 +789,8 @@ class MGXS(object):
                     std_dev = np.sqrt(std_dev)
 
             # Reshape condensed data arrays with one dimension for all filters
-            new_shape = \
-                (tally.num_filter_bins, tally.num_nuclides, tally.num_scores,)
-            mean = np.reshape(mean, new_shape)
-            std_dev = np.reshape(std_dev, new_shape)
+            mean = np.reshape(mean, tally.shape)
+            std_dev = np.reshape(std_dev, tally.shape)
 
             # Override tally's data with the new condensed data
             tally._mean = mean
@@ -873,10 +871,8 @@ class MGXS(object):
                 domain_filter.num_bins = 1
 
             # Reshape averaged data arrays with one dimension for all filters
-            new_shape = \
-                (tally.num_filter_bins, tally.num_nuclides, tally.num_scores,)
-            mean = np.reshape(mean, new_shape)
-            std_dev = np.reshape(std_dev, new_shape)
+            mean = np.reshape(mean, tally.shape)
+            std_dev = np.reshape(std_dev, tally.shape)
 
             # Override tally's data with the new condensed data
             tally._mean = mean
diff --git a/openmc/tallies.py b/openmc/tallies.py
index 8764e2e17c..3a8f102ce3 100644
--- a/openmc/tallies.py
+++ b/openmc/tallies.py
@@ -2841,12 +2841,6 @@ class Tally(object):
         new_tally = copy.deepcopy(self)
         new_tally.add_filter(new_filter)
 
-        # Determine the shape of data in the new diagonalized Tally
-        num_filter_bins = new_tally.num_filter_bins
-        num_nuclides = new_tally.num_nuclides
-        num_scores = new_tally.num_scores
-        new_shape = (num_filter_bins, num_nuclides, num_scores)
-
         # Determine "base" indices along the new "diagonal", and the factor
         # by which the "base" indices should be repeated to account for all
         # other filter bins in the diagonalized tally