diff --git a/ds/ringbuf.c b/ds/ringbuf.c
index 44dd5a5..acb7331 100644
--- a/ds/ringbuf.c
+++ b/ds/ringbuf.c
@@ -286,8 +286,8 @@ kern_status_t ringbuf_write(
 	kern_status_t status = KERN_OK;
 
 	while (remaining > 0) {
-		void *dest;
-		size_t available;
+		void *dest = NULL;
+		size_t available = 0;
 		wait_for_capacity(buf, irq_flags);
 
 		status = ringbuf_open_write_buffer(buf, &dest, &available);