diff --git a/dom/media/webvtt/vtt.jsm b/dom/media/webvtt/vtt.jsm
index 3e4696bc104e..a0093fbf51e4 100644
--- a/dom/media/webvtt/vtt.jsm
+++ b/dom/media/webvtt/vtt.jsm
@@ -1575,6 +1575,7 @@ XPCOMUtils.defineLazyPreferenceGetter(this, "DEBUG_LOG",
       }
 
       try {
+        LOG(`state=${self.state}, line=${line}`)
         // 5.1 WebVTT file parsing.
         if (self.state === "INITIAL") {
           parseSignatureMayThrow(line);