diff --git a/augur/titer_model.py b/augur/titer_model.py
index 92b213be0..734cc2675 100644
--- a/augur/titer_model.py
+++ b/augur/titer_model.py
@@ -226,7 +226,7 @@ def __init__(self, titers, **kwargs):
         else:
             self.titers = titers
             strain_counts = type(self).count_strains(titers)
-            self.strains = strain_counts.keys()
+            self.strains = list(strain_counts.keys())
 
     def read_titers(self, fname):
         self.titer_fname = fname
@@ -504,7 +504,7 @@ def validate(self, plot=False, cutoff=0.0, validation_set = None, fname=None):
             pred_titer = self.predict_titer(key[0], key[1], cutoff=cutoff)
             validation[key] = (val, pred_titer)
 
-        validation_array = np.array(validation.values())
+        validation_array = np.array(list(validation.values()))
         actual = validation_array[:,0]
         predicted = validation_array[:,1]
 
@@ -517,7 +517,7 @@ def validate(self, plot=False, cutoff=0.0, validation_set = None, fname=None):
                         'rms_error': np.sqrt(np.mean((actual-predicted)**2)),
         }
         pprint(model_performance)
-        model_performance['values'] = validation.values()
+        model_performance['values'] = list(validation.values())
 
         self.validation = model_performance