diff --git a/training/coqui_stt_training/util/config.py b/training/coqui_stt_training/util/config.py
index 0a04ad77..6bb35f3a 100755
--- a/training/coqui_stt_training/util/config.py
+++ b/training/coqui_stt_training/util/config.py
@@ -104,7 +104,11 @@ class _SttConfig(Coqpit):
         if not self.available_devices:
             self.available_devices = [self.cpu_device]
 
-        if self.bytes_output_mode:
+        if self.bytes_output_mode and self.alphabet_config_path:
+            raise RuntimeError(
+                "You cannot set --alphabet_config_path *and* --bytes_output_mode"
+            )
+        elif self.bytes_output_mode:
             self.alphabet = UTF8Alphabet()
         elif self.alphabet_config_path:
             self.alphabet = Alphabet(os.path.abspath(self.alphabet_config_path))