diff --git a/src/channel.c b/src/channel.c
index c5a51f7..1efab9c 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -205,7 +205,7 @@
 	if (unlikely(channel_input_closed(chn)))
 		return NULL;
 
-	if (!chn->buf->size || !buffer_empty(chn->buf))
+	if (!c_size(chn) || !c_empty(chn))
 		return buf;
 
 	old = chn->buf;