diff --git a/src/buffer.c b/src/buffer.c
index 91bee63..9037dd3 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -88,6 +88,11 @@
 	if (bi_end(b) + delta >= b->data + b->size)
 		return 0;  /* no space left */
 
+	if (buffer_not_empty(b) &&
+	    bi_end(b) + delta > bo_ptr(b) &&
+	    bo_ptr(b) >= bi_end(b))
+		return 0;  /* no space left before wrapping data */
+
 	/* first, protect the end of the buffer */
 	memmove(pos + delta, pos, bi_end(b) - pos);