diff --git a/mhcflurry/class1_presentation_neural_network.py b/mhcflurry/class1_presentation_neural_network.py
index 970c52867a9e687512da8a6d6a12b38d7dc610ac..e580e715705c109700f9c27c487837a645ebbb7f 100644
--- a/mhcflurry/class1_presentation_neural_network.py
+++ b/mhcflurry/class1_presentation_neural_network.py
@@ -453,7 +453,7 @@ class Class1PresentationNeuralNetwork(object):
 
         allele_representations_hash = self.set_allele_representations(
             allele_representations)
-        loss_reduction = "sum_over_batch_size"
+        loss_reduction = "sum"
         self.network.compile(
             loss=[
                 affinities_loss.get_keras_loss(reduction=loss_reduction),
@@ -846,4 +846,4 @@ class Class1PresentationNeuralNetwork(object):
             instance.network = keras.models.model_from_json(network_json)
             if weights is not None:
                 instance.network.set_weights(weights)
-        return instance
\ No newline at end of file
+        return instance