diff --git a/NEWS.md b/NEWS.md
index 93f9e9b3d..9315082c8 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -17,6 +17,9 @@
 * mkvinfo: when compiled with newer versions of the `fmt` library, certain
   numbers were not output correctly (e.g. a track's audio sampling frequency
   of 48000 might be output as 48).
+* MKVToolNix GUI: multiplexer: deriving the track language from the file name
+  will match languages case insensitively again (like versions prior to
+  v55). Fixes #3068.
 
 ## Build system changes
 
diff --git a/src/mkvtoolnix-gui/merge/source_file.cpp b/src/mkvtoolnix-gui/merge/source_file.cpp
index a8ffb780e..115f612e3 100644
--- a/src/mkvtoolnix-gui/merge/source_file.cpp
+++ b/src/mkvtoolnix-gui/merge/source_file.cpp
@@ -356,8 +356,8 @@ SourceFile::setupProgramMapFromProperties() {
 mtx::bcp47::language_c
 SourceFile::deriveLanguageFromFileName() {
   auto &cfg     = Util::Settings::get();
-  auto fileName = QFileInfo{m_fileName}.fileName();
-  auto matches  = QRegularExpression{Q("s\\d+e\\d{2,}(.+)"), QRegularExpression::CaseInsensitiveOption}.match(fileName);
+  auto fileName = QFileInfo{m_fileName}.fileName().toLower();
+  auto matches  = QRegularExpression{Q("s\\d+e\\d{2,}(.+)")}.match(fileName);
 
   if (matches.hasMatch()) {
     fileName = matches.captured(1);