diff --git a/src/effects/DtmfGen.cpp b/src/effects/DtmfGen.cpp
index cd47be61b..140e3d129 100644
--- a/src/effects/DtmfGen.cpp
+++ b/src/effects/DtmfGen.cpp
@@ -133,6 +133,8 @@ unsigned EffectDtmf::GetAudioOutCount()
 
 bool EffectDtmf::ProcessInitialize(sampleCount WXUNUSED(totalLen), ChannelNames WXUNUSED(chanMap))
 {
+   if (dtmfNTones <= 0)   // Bail if no DTFM sequence.
+      return false;
    double duration = GetDuration();
 
    // all dtmf sequence durations in samples from seconds