diff --git a/whisper/transcribe.py b/whisper/transcribe.py
index c228800..911f36c 100644
--- a/whisper/transcribe.py
+++ b/whisper/transcribe.py
@@ -208,6 +208,7 @@ def transcribe(
             if (
                 no_speech_threshold is not None
                 and decode_result.no_speech_prob > no_speech_threshold
+                and logprob_threshold is not None
                 and decode_result.avg_logprob < logprob_threshold
             ):
                 needs_fallback = False  # silence