diff --git a/audio/filter/af_hrtf.c b/audio/filter/af_hrtf.c
index 4fb382aff4..5dc08f2dbf 100644
--- a/audio/filter/af_hrtf.c
+++ b/audio/filter/af_hrtf.c
@@ -280,8 +280,13 @@ static inline void update_ch(af_hrtf_t *s, short *in, const int k)
     }
 
     /* We need to update the bass compensation delay line, too. */
-    s->ba_l[k] = in[0] + in[4] + in[2];
-    s->ba_r[k] = in[4] + in[1] + in[3];
+    // TODO: should this use lf/cf/rf etc. instead?
+    s->ba_l[k] = in[0];
+    s->ba_r[k] = in[1];
+    if (s->decode_mode == HRTF_MIX_51) {
+        s->ba_l[k] += in[4] + in[2];
+        s->ba_r[k] += in[4] + in[3];
+    }
 }
 
 static void clear_coeff(af_hrtf_t *s, float *c)