diff --git a/ringbuffer.c b/ringbuffer.c
index 3edab0d..964ab43 100644
--- a/ringbuffer.c
+++ b/ringbuffer.c
@@ -108,7 +108,7 @@
 	free(rbc);
 }
 
-static size_t ringbuffer_len(struct ringbuffer_consumer *rbc)
+size_t ringbuffer_len(struct ringbuffer_consumer *rbc)
 {
 	if (rbc->pos <= rbc->rb->tail)
 		return rbc->rb->tail - rbc->pos;
@@ -148,6 +148,9 @@
 	if (len >= rb->size)
 		return -1;
 
+	if (len == 0)
+		return 0;
+
 	/* Ensure there is at least len bytes of space available.
 	 *
 	 * If a client doesn't have sufficient space, perform a blocking write
@@ -176,6 +179,7 @@
 	memcpy(rb->buf, data, len);
 	rb->tail += len;
 
+
 	/* Inform consumers of new data in non-blocking mode, by calling
 	 * ->poll_fn with 0 force_len */
 	for (i = 0; i < rb->n_consumers; i++) {