diff --git a/AudioMixer4_F32.cpp b/AudioMixer4_F32.cpp
index 40e9757..acab10f 100644
--- a/AudioMixer4_F32.cpp
+++ b/AudioMixer4_F32.cpp
@@ -6,7 +6,7 @@ void AudioMixer4_F32::update(void) {
   out = receiveWritable_f32(0);
   if (!out) return;
 
-  arm_scale_f32(out->data, multiplier[0], out->data, AUDIO_BLOCK_SAMPLES);
+  arm_scale_f32(out->data, multiplier[0], out->data, out->length);
 
   for (int channel=1; channel < 4; channel++) {
     in = receiveReadOnly_f32(channel);
@@ -16,8 +16,8 @@ void AudioMixer4_F32::update(void) {
 
     audio_block_f32_t *tmp = allocate_f32();
 
-    arm_scale_f32(in->data, multiplier[channel], tmp->data, AUDIO_BLOCK_SAMPLES);
-    arm_add_f32(out->data, tmp->data, out->data, AUDIO_BLOCK_SAMPLES);
+    arm_scale_f32(in->data, multiplier[channel], tmp->data, tmp->length);
+    arm_add_f32(out->data, tmp->data, out->data, tmp->length);
 
     release(tmp);
     release(in);