diff --git a/NEWS.md b/NEWS.md
index 3974e820f..f7e421522 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -6,6 +6,15 @@
   Wikipedia's "List of languages by native speakers" by default. Also by
   default only those languages will be shown in the language drop-down boxes.
 
+## Bug fixes
+
+* MKVToolNix GUI: multiplexer: fixed a bug in the "make destination file names
+  unique" logic that caused an existing number-in-parenthesis at the end of
+  the file base name to be removed in certain situations (e.g. when the first
+  added file was named `m (3).mkv` and both `m (3) (1).mkv` and `m (3)
+  (2).mkv` existed already, the GUI was suddenly use `m.mkv` instead of `m (3)
+  (3).mkv`).
+
 
 # Version 36.0.0 "Is That Jazz?" 2019-08-10
 
diff --git a/src/mkvtoolnix-gui/merge/input.cpp b/src/mkvtoolnix-gui/merge/input.cpp
index 988a2d1ab..b0b475891 100644
--- a/src/mkvtoolnix-gui/merge/input.cpp
+++ b/src/mkvtoolnix-gui/merge/input.cpp
@@ -1562,13 +1562,19 @@ Tab::setOutputFileNameMaybe(bool force) {
 
 QString
 Tab::generateUniqueOutputFileName(QString const &baseName,
-                                  QDir const &outputDir) {
+                                  QDir const &outputDir,
+                                  bool removeUniquenessSuffix) {
   auto &settings       = Util::Settings::get();
   auto cleanedBaseName = baseName;
   auto suffix          = suggestOutputFileNameExtension();
+  auto needToRemove    =    removeUniquenessSuffix
+                         && !m_config.m_destinationUniquenessSuffix.isEmpty()
+                         && cleanedBaseName.endsWith(m_config.m_destinationUniquenessSuffix);
 
-  if (   !m_config.m_destinationUniquenessSuffix.isEmpty()
-      && cleanedBaseName.endsWith(m_config.m_destinationUniquenessSuffix))
+  qDebug() << "generateUniqueOutputFileName: baseName" << baseName << "suffix" << suffix << "destinationUniquenessSuffix" << m_config.m_destinationUniquenessSuffix
+           << "removeUniquenessSuffix" << removeUniquenessSuffix << "needToRemove" << needToRemove;
+
+  if (needToRemove)
     cleanedBaseName.remove(cleanedBaseName.length() - m_config.m_destinationUniquenessSuffix.length(), m_config.m_destinationUniquenessSuffix.length());
 
   auto idx = 0;
diff --git a/src/mkvtoolnix-gui/merge/output.cpp b/src/mkvtoolnix-gui/merge/output.cpp
index 74d869a72..4c13dfe5b 100644
--- a/src/mkvtoolnix-gui/merge/output.cpp
+++ b/src/mkvtoolnix-gui/merge/output.cpp
@@ -720,7 +720,7 @@ Tab::changeOutputDirectoryTo(QString const &directory) {
   auto makeUnique  = Util::Settings::get().m_uniqueOutputFileNames;
   auto oldFileName = QFileInfo{ m_config.m_destination }.fileName();
   auto newFileName = !oldFileName.isEmpty() ? oldFileName : Q("%1.%2").arg(QY("unnamed")).arg(suggestOutputFileNameExtension());
-  auto newFilePath = makeUnique ? generateUniqueOutputFileName(QFileInfo{newFileName}.completeBaseName(), QDir{directory}) : Q("%1/%2").arg(directory).arg(newFileName);
+  auto newFilePath = makeUnique ? generateUniqueOutputFileName(QFileInfo{newFileName}.completeBaseName(), QDir{directory}, true) : Q("%1/%2").arg(directory).arg(newFileName);
 
   ui->output->setText(QDir::toNativeSeparators(newFilePath));
 }
diff --git a/src/mkvtoolnix-gui/merge/tab.h b/src/mkvtoolnix-gui/merge/tab.h
index 58fbd7f5c..2ebb7718b 100644
--- a/src/mkvtoolnix-gui/merge/tab.h
+++ b/src/mkvtoolnix-gui/merge/tab.h
@@ -332,7 +332,7 @@ protected:
 
   virtual void setOutputFileNameMaybe(bool force = false);
   virtual QString suggestOutputFileNameExtension() const;
-  virtual QString generateUniqueOutputFileName(QString const &baseName, QDir const &outputDir);
+  virtual QString generateUniqueOutputFileName(QString const &baseName, QDir const &outputDir, bool removeUniquenessSuffix = false);
 
   virtual void enableDisableAllTracks(bool enable);