diff --git a/synthesize.py b/synthesize.py
index cb0ee8af..eec022ab 100644
--- a/synthesize.py
+++ b/synthesize.py
@@ -31,8 +31,8 @@ def tts(model,
         postnet_output = ap.out_linear_to_mel(postnet_output.T).T
     # correct if there is a scale difference b/w two models
     postnet_output = ap._denormalize(postnet_output)
-    postnet_output = ap_vocoder._normalize(postnet_output)
     if use_vocoder_model:
+        postnet_output = ap_vocoder._normalize(postnet_output)
         vocoder_input = torch.FloatTensor(postnet_output.T).unsqueeze(0)
         waveform = vocoder_model.generate(
             vocoder_input.cuda() if use_cuda else vocoder_input,