diff --git a/libaf/af.c b/libaf/af.c
index 0bc783e49c..bc7a92a56b 100644
--- a/libaf/af.c
+++ b/libaf/af.c
@@ -694,5 +694,9 @@ void af_help (void) {
 
 void af_fix_parameters(af_data_t *data)
 {
+    if (data->nch < 0 || data->nch > AF_NCH) {
+      mp_msg(MSGT_AFILTER, MSGL_ERR, "Invalid number of channels %i, assuming 2.\n", data->nch);
+      data->nch = 2;
+    }
     data->bps = af_fmt2bits(data->format)/8;
 }