diff --git a/include/common/istbuf.h b/include/common/istbuf.h
index 2210d4a..7631212 100644
--- a/include/common/istbuf.h
+++ b/include/common/istbuf.h
@@ -98,7 +98,7 @@
 		return r.len < b->size ? 0 : -1;
 
 	p = b_tail(b);
-	b->len += r.len;
+	b->data += r.len;
 	while (r.len--) {
 		*p++ = *r.ptr++;
 		if (unlikely(p == end))