diff --git a/facelib/TernausNet.py b/facelib/TernausNet.py
index 00a807e..1efab9e 100644
--- a/facelib/TernausNet.py
+++ b/facelib/TernausNet.py
@@ -19,7 +19,7 @@ TernausNet: U-Net with VGG11 Encoder Pre-Trained on ImageNet for Image Segmentat
 
 class TernausNet(object):
     VERSION = 1
-    def __init__ (self, name, resolution, face_type_str, load_weights=True, weights_file_root=None, training=False, place_model_on_cpu=False):
+    def __init__ (self, name, resolution, face_type_str=None, load_weights=True, weights_file_root=None, training=False, place_model_on_cpu=False):
         nn.initialize(data_format="NHWC")
         tf = nn.tf
 
@@ -125,12 +125,16 @@ class TernausNet(object):
             self.net = Ternaus(3, 64, name='Ternaus')
             self.net_weights = self.net.get_weights()
 
-        self.model_filename_list = [ [self.net, '%s_%d_%s.npy' % (name, resolution, face_type_str) ] ]
+        model_name = f'{name}_{resolution}'        
+        if face_type_str is not None:
+            model_name += f'_{face_type_str}'            
+
+        self.model_filename_list = [ [self.net, f'{model_name}.npy'] ]
 
         if training:
             self.opt = nn.TFRMSpropOptimizer(lr=0.0001, name='opt')
             self.opt.initialize_variables (self.net_weights, vars_on_cpu=place_model_on_cpu)
-            self.model_filename_list += [ [self.opt, '%s_%d_%s_opt.npy' % (name, resolution, face_type_str) ] ]
+            self.model_filename_list += [ [self.opt, f'{model_name}_opt.npy' ] ]
         else:
             _, pred = self.net([self.input_t])
             def net_run(input_np):