diff --git a/rbd/rbd.go b/rbd/rbd.go
index 5b1a1e5..5b77aae 100644
--- a/rbd/rbd.go
+++ b/rbd/rbd.go
@@ -955,7 +955,7 @@ func (image *Image) Discard(ofs uint64, length uint64) (int, error) {
 	return int(ret), nil
 }
 
-func (image *Image) ReadAt(data []byte, off int64) (n int, err error) {
+func (image *Image) ReadAt(data []byte, off int64) (int, error) {
 	if err := image.validate(imageIsOpen); err != nil {
 		return 0, err
 	}
@@ -974,7 +974,7 @@ func (image *Image) ReadAt(data []byte, off int64) (n int, err error) {
 		return 0, RBDError(ret)
 	}
 
-	if ret < n {
+	if ret < len(data) {
 		return ret, io.EOF
 	}