diff --git a/gst/isomp4/atoms.h b/gst/isomp4/atoms.h
index c448cd7696..d256847950 100644
--- a/gst/isomp4/atoms.h
+++ b/gst/isomp4/atoms.h
@@ -953,7 +953,7 @@ void atom_moov_add_3gp_tag           (AtomMOOV * moov, guint32 fourcc, guint8 *
 
 void atom_moov_add_xmp_tags          (AtomMOOV * moov, GstBuffer * xmp);
 
-#define GST_QT_MUX_DEFAULT_TAG_LANGUAGE   "eng"
+#define GST_QT_MUX_DEFAULT_TAG_LANGUAGE   "und" /* undefined/unknown */
 guint16  language_code               (const char * lang);
 
 #endif /* __ATOMS_H__ */