diff --git a/spa/plugins/audioconvert/channelmix-ops.c b/spa/plugins/audioconvert/channelmix-ops.c
index 76b1c701a..1ec172eb7 100644
--- a/spa/plugins/audioconvert/channelmix-ops.c
+++ b/spa/plugins/audioconvert/channelmix-ops.c
@@ -549,6 +549,10 @@ int channelmix_init(struct channelmix *mix)
 {
 	const struct channelmix_info *info;
 
+	if (mix->src_chan > SPA_AUDIO_MAX_CHANNELS ||
+	    mix->dst_chan > SPA_AUDIO_MAX_CHANNELS)
+		return -EINVAL;
+
 	info = find_channelmix_info(mix->src_chan, mix->src_mask, mix->dst_chan, mix->dst_mask,
 			mix->cpu_flags);
 	if (info == NULL)
diff --git a/spa/plugins/audioconvert/channelmix-ops.h b/spa/plugins/audioconvert/channelmix-ops.h
index 08951267c..d43eafa4e 100644
--- a/spa/plugins/audioconvert/channelmix-ops.h
+++ b/spa/plugins/audioconvert/channelmix-ops.h
@@ -43,8 +43,6 @@
 #define MASK_5_1	_M(FL)|_M(FR)|_M(FC)|_M(LFE)|_M(SL)|_M(SR)|_M(RL)|_M(RR)
 #define MASK_7_1	_M(FL)|_M(FR)|_M(FC)|_M(LFE)|_M(SL)|_M(SR)|_M(RL)|_M(RR)
 
-#define BUFFER_SIZE 4096
-
 #define BUFFER_SIZE 4096
 #define MAX_TAPS 255