diff --git a/autotune.go b/autotune.go
index b18e8a29..e037580b 100644
--- a/autotune.go
+++ b/autotune.go
@@ -37,7 +37,10 @@ type autoTune struct {
 
 // Sample adds a signal sample to the pulse buffer
 func (tune *autoTune) Sample(bit bool, seq uint32) {
-	tune.pulses[seq%maxAutoTuneSamples] = pulse{bit, seq}
+	// ensure seq is in range [pulses[0].seq, pulses[0].seq + maxAutoTuneSamples]
+	if seq >= tune.pulses[0].seq && seq <= tune.pulses[0].seq+maxAutoTuneSamples {
+		tune.pulses[seq%maxAutoTuneSamples] = pulse{bit, seq}
+	}
 }
 
 // Find a period for a given signal
diff --git a/autotune_test.go b/autotune_test.go
index 75e61696..2c933c27 100644
--- a/autotune_test.go
+++ b/autotune_test.go
@@ -66,4 +66,20 @@ func TestAutoTune(t *testing.T) {
 	}
 	assert.Equal(t, -1, tune.FindPeriod(true))
 	assert.Equal(t, 4, tune.FindPeriod(false))
+
+	// minimal test
+	tune = autoTune{}
+	for i := 0; i < 1024; i++ {
+		if i%maxAutoTuneSamples == 0 {
+			tune.Sample(false, uint32(i))
+		} else {
+			tune.Sample(true, uint32(i))
+		}
+	}
+	assert.NotEqual(t, 0, tune.pulses[0].seq)
+	minSeq := tune.pulses[0].seq
+	t.Log("minimal seq", tune.pulses[0].seq)
+
+	tune.Sample(false, minSeq-1)
+	assert.Equal(t, minSeq, tune.pulses[0].seq)
 }