diff --git a/src/article_maker.cc b/src/article_maker.cc
index eab66e6c..9558ac41 100644
--- a/src/article_maker.cc
+++ b/src/article_maker.cc
@@ -315,7 +315,7 @@ sptr< Dictionary::DataRequest > ArticleMaker::makeDefinitionFor( QString const &
                                                true );
   }
 
-  if ( groupId == Instances::Group::HelpGroupId ) {
+  if ( groupId == GroupId::HelpGroupId ) {
     if ( word == tr( "Welcome!" ) ) {
       string welcome                           = makeWelcomeHtml();
       sptr< Dictionary::DataRequestInstant > r = std::make_shared< Dictionary::DataRequestInstant >( true );
diff --git a/src/config.hh b/src/config.hh
index 1a5feaac..bc4c960d 100644
--- a/src/config.hh
+++ b/src/config.hh
@@ -18,6 +18,13 @@
 #include <optional>
 #include <QThread>
 
+/// Special group IDs
+enum GroupId : unsigned {
+  AllGroupId  = UINT_MAX - 1, /// The 'All' group
+  HelpGroupId = UINT_MAX,     /// The fictitious 'Help' group
+  NoGroupId   = 0,            /// Invalid value, used to specify that no group id is specified at all.
+};
+
 /// GoldenDict's configuration
 namespace Config {
 
diff --git a/src/fulltextsearch.cc b/src/fulltextsearch.cc
index 5f14613d..edfb815f 100644
--- a/src/fulltextsearch.cc
+++ b/src/fulltextsearch.cc
@@ -494,7 +494,7 @@ void FullTextSearchDialog::updateDictionaries()
   Config::Group const * grp = cfg.getGroup( group );
   Config::MutedDictionaries const * mutedDicts;
 
-  if ( group == Instances::Group::AllGroupId ) {
+  if ( group == GroupId::AllGroupId ) {
     mutedDicts = &cfg.mutedDictionaries;
   }
   else {
diff --git a/src/instances.hh b/src/instances.hh
index 56a87d28..6718ac0a 100644
--- a/src/instances.hh
+++ b/src/instances.hh
@@ -45,17 +45,6 @@ struct Group
 
   /// Remove id's if not presented in group dictionaries
   void checkMutedDictionaries( Config::MutedDictionaries * mutedDictionaries ) const;
-
-  // Some constants
-
-  /// The id of the 'All' group
-  static const unsigned AllGroupId = UINT_MAX - 1;
-
-  /// The id of the fictious 'Help' group
-  static const unsigned HelpGroupId = UINT_MAX;
-
-  /// Invalid value, used to specify that no group id is specified at all.
-  static const unsigned NoGroupId = 0;
 };
 
 struct Groups: public vector< Group >
diff --git a/src/ui/articleview.cc b/src/ui/articleview.cc
index 722fde5a..cf03b557 100644
--- a/src/ui/articleview.cc
+++ b/src/ui/articleview.cc
@@ -798,7 +798,7 @@ QStringList ArticleView::getMutedDictionaries( unsigned group )
     // Find muted dictionaries for current group
     Config::Group const * grp = cfg.getGroup( group );
     Config::MutedDictionaries const * mutedDictionaries;
-    if ( group == Instances::Group::AllGroupId ) {
+    if ( group == GroupId::AllGroupId ) {
       mutedDictionaries = popupView ? &cfg.popupMutedDictionaries : &cfg.mutedDictionaries;
     }
     else {
@@ -1766,7 +1766,7 @@ void ArticleView::pasteTriggered()
 
   if ( !word.isEmpty() ) {
     unsigned groupId = getGroup( webview->url() );
-    if ( groupId == 0 || groupId == Instances::Group::HelpGroupId ) {
+    if ( groupId == 0 || groupId == GroupId::HelpGroupId ) {
       // We couldn't figure out the group out of the URL,
       // so let's try the currently selected group.
       groupId = currentGroupId;
@@ -1918,7 +1918,7 @@ void ArticleView::doubleClicked( QPoint pos )
         QUrl const & ref = webview->url();
 
         auto groupId = getGroup( ref );
-        if ( groupId == 0 || groupId == Instances::Group::HelpGroupId ) {
+        if ( groupId == 0 || groupId == GroupId::HelpGroupId ) {
           groupId = currentGroupId;
         }
         if ( Utils::Url::hasQueryItem( ref, "dictionaries" ) ) {
@@ -2062,7 +2062,7 @@ void ArticleView::setActiveDictIds( const ActiveDictIds & ad )
 {
   auto groupId = ad.groupId;
   if ( groupId == 0 ) {
-    groupId = Instances::Group::AllGroupId;
+    groupId = GroupId::AllGroupId;
   }
   if ( ( ad.word == currentWord && groupId == getCurrentGroup() ) || historyMode ) {
     // ignore all other signals.
@@ -2077,7 +2077,7 @@ void ArticleView::dictionaryClear( const ActiveDictIds & ad )
 {
   auto groupId = ad.groupId;
   if ( groupId == 0 ) {
-    groupId = Instances::Group::AllGroupId;
+    groupId = GroupId::AllGroupId;
   }
   // ignore all other signals.
   if ( ad.word == currentWord && groupId == getCurrentGroup() ) {
diff --git a/src/ui/editdictionaries.cc b/src/ui/editdictionaries.cc
index ceeac7f2..40d37a5a 100644
--- a/src/ui/editdictionaries.cc
+++ b/src/ui/editdictionaries.cc
@@ -74,7 +74,7 @@ void EditDictionaries::editGroup( unsigned id )
 {
   ui.tabs->setTabVisible( 0, false );
 
-  if ( id == Instances::Group::AllGroupId ) {
+  if ( id == GroupId::AllGroupId ) {
     ui.tabs->setCurrentIndex( 1 );
   }
   else {
diff --git a/src/ui/mainwindow.cc b/src/ui/mainwindow.cc
index 4c60632a..b5de33bb 100644
--- a/src/ui/mainwindow.cc
+++ b/src/ui/mainwindow.cc
@@ -553,7 +553,7 @@ MainWindow::MainWindow( Config::Class & cfg_ ):
   // Dictionary bar
 
   Instances::Group const * igrp = groupInstances.findGroup( cfg.lastMainGroupId );
-  if ( cfg.lastMainGroupId == Instances::Group::AllGroupId ) {
+  if ( cfg.lastMainGroupId == GroupId::AllGroupId ) {
     if ( igrp ) {
       igrp->checkMutedDictionaries( &cfg.mutedDictionaries );
     }
@@ -776,7 +776,7 @@ MainWindow::MainWindow( Config::Class & cfg_ ):
   addNewTab();
   ArticleView * view = getCurrentArticleView();
   history.enableAdd( false );
-  view->showDefinition( tr( "Welcome!" ), Instances::Group::HelpGroupId );
+  view->showDefinition( tr( "Welcome!" ), GroupId::HelpGroupId );
   history.enableAdd( cfg.preferences.storeHistory );
 
   // restore should be called after all UI initialized but not necessarily after show()
@@ -1640,7 +1640,7 @@ void MainWindow::updateGroupList( bool reload )
                                           dictionaries );
 
     g.name = tr( "All" );
-    g.id   = Instances::Group::AllGroupId;
+    g.id   = GroupId::AllGroupId;
     g.icon = "folder.png";
 
     groupInstances.push_back( g );
@@ -1685,7 +1685,7 @@ void MainWindow::updateDictionaryBar()
 
   dictionaryBar.setMutedDictionaries( nullptr );
   if ( grp ) { // Should always be !0, but check as a safeguard
-    if ( currentId == Instances::Group::AllGroupId ) {
+    if ( currentId == GroupId::AllGroupId ) {
       dictionaryBar.setMutedDictionaries( &cfg.mutedDictionaries );
     }
     else {
@@ -2205,7 +2205,7 @@ void MainWindow::editDictionaries( unsigned editDictionaryGroup )
 
     connect( &dicts, &EditDictionaries::showDictionaryHeadwords, this, &MainWindow::showDictionaryHeadwords );
 
-    if ( editDictionaryGroup != Instances::Group::NoGroupId ) {
+    if ( editDictionaryGroup != GroupId::NoGroupId ) {
       dicts.editGroup( editDictionaryGroup );
     }
 
@@ -2219,7 +2219,7 @@ void MainWindow::editDictionaries( unsigned editDictionaryGroup )
       // Set muted dictionaries from old groups
       for ( auto & group : newCfg.groups ) {
         unsigned id = group.id;
-        if ( id != Instances::Group::NoGroupId ) {
+        if ( id != GroupId::NoGroupId ) {
           Config::Group const * grp = cfg.getGroup( id );
           if ( grp ) {
             group.mutedDictionaries      = grp->mutedDictionaries;
@@ -2373,7 +2373,7 @@ void MainWindow::currentGroupChanged( int )
   unsigned grg_id               = groupList->getCurrentGroup();
   cfg.lastMainGroupId           = grg_id;
   Instances::Group const * igrp = groupInstances.findGroup( grg_id );
-  if ( grg_id == Instances::Group::AllGroupId ) {
+  if ( grg_id == GroupId::AllGroupId ) {
     if ( igrp ) {
       igrp->checkMutedDictionaries( &cfg.mutedDictionaries );
     }
diff --git a/src/ui/mainwindow.hh b/src/ui/mainwindow.hh
index 007f8cfb..1cc0e145 100644
--- a/src/ui/mainwindow.hh
+++ b/src/ui/mainwindow.hh
@@ -345,7 +345,7 @@ private slots:
 
   /// If editDictionaryGroup is specified, the dialog positions on that group
   /// initially.
-  void editDictionaries( unsigned editDictionaryGroup = Instances::Group::NoGroupId );
+  void editDictionaries( unsigned editDictionaryGroup = GroupId::NoGroupId );
   /// Edits current group when triggered from the dictionary bar.
   void editCurrentGroup();
   void editPreferences();
diff --git a/src/ui/scanpopup.cc b/src/ui/scanpopup.cc
index a5d61d82..27328193 100644
--- a/src/ui/scanpopup.cc
+++ b/src/ui/scanpopup.cc
@@ -140,7 +140,7 @@ ScanPopup::ScanPopup( QWidget * parent,
   dictionaryBar.setFloatable( false );
 
   Instances::Group const * igrp = groups.findGroup( cfg.lastPopupGroupId );
-  if ( cfg.lastPopupGroupId == Instances::Group::AllGroupId ) {
+  if ( cfg.lastPopupGroupId == GroupId::AllGroupId ) {
     if ( igrp ) {
       igrp->checkMutedDictionaries( &cfg.popupMutedDictionaries );
     }
@@ -591,7 +591,7 @@ void ScanPopup::currentGroupChanged( int )
 {
   cfg.lastPopupGroupId          = ui.groupList->getCurrentGroup();
   Instances::Group const * igrp = groups.findGroup( cfg.lastPopupGroupId );
-  if ( cfg.lastPopupGroupId == Instances::Group::AllGroupId ) {
+  if ( cfg.lastPopupGroupId == GroupId::AllGroupId ) {
     if ( igrp ) {
       igrp->checkMutedDictionaries( &cfg.popupMutedDictionaries );
     }
@@ -1086,7 +1086,7 @@ void ScanPopup::updateDictionaryBar()
     dictionaryBar.setDictionaries( grp->dictionaries );
   }
 
-  if ( currentId == Instances::Group::AllGroupId ) {
+  if ( currentId == GroupId::AllGroupId ) {
     dictionaryBar.setMutedDictionaries( &cfg.popupMutedDictionaries );
   }
   else {