diff --git a/common/crypto/auth.go b/common/crypto/auth.go
index 71a0c91ad..c3d431b43 100644
--- a/common/crypto/auth.go
+++ b/common/crypto/auth.go
@@ -52,6 +52,7 @@ func (v *AuthenticationReader) NextChunk() error {
 		return err
 	}
 	v.chunk = plainChunk
+	v.buffer.SliceFrom(size + 2)
 	return nil
 }