diff --git a/src/ui/Features/Main/MainViewModel.cs b/src/ui/Features/Main/MainViewModel.cs
index f05e942c96..dbaa096be7 100644
--- a/src/ui/Features/Main/MainViewModel.cs
+++ b/src/ui/Features/Main/MainViewModel.cs
@@ -6003,6 +6003,10 @@ private async Task ShowSpeechToTextWhisper()
             SetSubtitles(_subtitle);
             SelectAndScrollToRow(0);
             ShowStatus(string.Format(Se.Language.Main.TranscriptionCompletedWithXLines, _subtitle.Paragraphs.Count));
+
+            // The subtitle content (and so its language) just changed without a
+            // file open, so re-evaluate the live spell check dictionary.
+            SetupLiveSpellCheck();
         }
         else if (result.OkPressed && result.IsBatchMode && result.BatchItems.Count == 1)
         {
@@ -6088,6 +6092,10 @@ private async Task ShowVideoOcr()
             SetSubtitles(_subtitle);
             SelectAndScrollToRow(0);
             ShowStatus(string.Format(Se.Language.Video.VideoOcr.LinesFoundX, _subtitle.Paragraphs.Count));
+
+            // The subtitle content (and so its language) just changed without a
+            // file open, so re-evaluate the live spell check dictionary.
+            SetupLiveSpellCheck();
         }
     }
 
@@ -15464,8 +15472,17 @@ await MessageBox.Show(Window!, Se.Language.General.Error, "This file seems to be
     private void SetupLiveSpellCheck()
     {
         var dictionaryFound = false;
-        var twoLetterLanguageCode = LanguageAutoDetect.AutoDetectGoogleLanguage(GetUpdateSubtitle());
-        var threeLetterLanguageCode = Iso639Dash2LanguageCode.GetThreeLetterCodeFromTwoLetterCode(twoLetterLanguageCode);
+
+        // Use the detection variant that returns null for an empty or undetectable
+        // subtitle. The regular variant falls back to English, which armed the
+        // spell checker with the English dictionary on an empty subtitle at
+        // startup; content arriving later without a file open (for example a
+        // transcription in a language with no dictionary installed) was then
+        // checked against English, underlining every word.
+        var twoLetterLanguageCode = LanguageAutoDetect.AutoDetectGoogleLanguageOrNull(GetUpdateSubtitle());
+        var threeLetterLanguageCode = string.IsNullOrEmpty(twoLetterLanguageCode)
+            ? null
+            : Iso639Dash2LanguageCode.GetThreeLetterCodeFromTwoLetterCode(twoLetterLanguageCode);
         if (!string.IsNullOrEmpty(threeLetterLanguageCode))
         {
             var spellCheckLanguages = _spellCheckManager.GetDictionaryLanguages(Se.DictionariesFolder);