reader.go | 1 +

diff --git a/reader.go b/reader.go
index d55571fc027bbc62866d74341786a07d6e5989fd..00c3ff32c4c8d5fe5739c837fe6222ebe11f1ca1 100644
--- a/reader.go
+++ b/reader.go
@@ -89,6 +89,7 @@ }
 
 // How many bytes are available to read. Max is the most we could require.
 func (r *reader) available(off, max int64) (ret int64) {
+	off += r.offset
 	for max > 0 {
 		req, ok := r.t.offsetRequest(off)
 		if !ok {