diff --git a/kernel/relay.c b/kernel/relay.c
index 6825b84..a4d6889 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -992,7 +992,8 @@
 	size_t subbuf_size = buf->chan->subbuf_size;
 	size_t n_subbufs = buf->chan->n_subbufs;
 	size_t consumed = buf->subbufs_consumed % n_subbufs;
-	size_t read_pos = consumed * subbuf_size + buf->bytes_consumed;
+	size_t read_pos = (consumed * subbuf_size + buf->bytes_consumed)
+			% (n_subbufs * subbuf_size);
 
 	read_subbuf = read_pos / subbuf_size;
 	padding = buf->padding[read_subbuf];