--- a/browser/components/translation/TranslationContentHandler.jsm
+++ b/browser/components/translation/TranslationContentHandler.jsm
@@ -80,18 +80,25 @@ TranslationContentHandler.prototype = {
     encoder.init(content.document, "text/plain", encoder.SkipInvisibleContent);
     let string = encoder.encodeToStringWithMaxLength(60 * 1024);
 
     // Language detection isn't reliable on very short strings.
     if (string.length < 100)
       return;
 
     LanguageDetector.detectLanguage(string).then(result => {
-      if (!result.confident)
+      // Bail if we're not confident.
+      if (!result.confident) {
         return;
+      }
+
+      // The window might be gone by now.
+      if (Cu.isDeadWrapper(content)) {
+        return;
+      }
 
       content.detectedLanguage = result.language;
 
       let data = {
         state: STATE_OFFER,
         originalShown: true,
         detectedLanguage: result.language
       };