diff --git a/mhcflurry/class1_neural_network.py b/mhcflurry/class1_neural_network.py
index eb621f8c0374993667a0b6207f36010aae1504e1..411ba54d24d4f04d74cd71efa7f82992db986ce9 100644
--- a/mhcflurry/class1_neural_network.py
+++ b/mhcflurry/class1_neural_network.py
@@ -1321,7 +1321,7 @@ class Class1NeuralNetwork(object):
                          peptide_allele_merge_activation)(current_layer)
 
         densenet_layers = [] if topology == "densenet" else None
-        for (i, layer_size) in enumerate(layer_size):
+        for (i, layer_size) in enumerate(layer_sizes):
             if densenet_layers is not None:
                 densenet_layers.append(current_layer)
                 if len(densenet_layers) > 1: