diff --git a/qskconfig.pri b/qskconfig.pri
index 3597a6d9..207cb5c2 100644
--- a/qskconfig.pri
+++ b/qskconfig.pri
@@ -55,6 +55,7 @@ linux-g++ | linux-g++-64 {
         }
     }
 
+    DEFINES += QT_STRICT_ITERATORS
 
     # --- optional debug options
 
diff --git a/src/controls/QskShortcut.cpp b/src/controls/QskShortcut.cpp
index f11bd2bd..d15e68c5 100644
--- a/src/controls/QskShortcut.cpp
+++ b/src/controls/QskShortcut.cpp
@@ -103,7 +103,7 @@ bool QskShortcutHandler::event( QEvent* event )
     {
         const QShortcutEvent* se = static_cast< const QShortcutEvent* >( event );
 
-        const auto it = m_invokeDataMap.find( se->shortcutId() );
+        const auto it = m_invokeDataMap.constFind( se->shortcutId() );
         if ( it != m_invokeDataMap.constEnd() )
         {
             const InvokeData& data = ( *it );
diff --git a/src/controls/QskStatusIndicator.cpp b/src/controls/QskStatusIndicator.cpp
index 0361fa9f..e399b7fb 100644
--- a/src/controls/QskStatusIndicator.cpp
+++ b/src/controls/QskStatusIndicator.cpp
@@ -229,7 +229,7 @@ void QskStatusIndicator::setStatus( int status )
     if ( status == m_data->currentStatus )
         return;
 
-    const auto it = m_data->map.find( status );
+    const auto it = m_data->map.constFind( status );
     if ( it == m_data->map.constEnd() )
     {
         qWarning() << "QskStatusIndicator: invalid status:" << status;
diff --git a/src/graphic/QskGraphicProviderMap.cpp b/src/graphic/QskGraphicProviderMap.cpp
index a3f6c23f..221eeda0 100644
--- a/src/graphic/QskGraphicProviderMap.cpp
+++ b/src/graphic/QskGraphicProviderMap.cpp
@@ -50,7 +50,7 @@ void QskGraphicProviderMap::insert(
 void QskGraphicProviderMap::remove( const QString& providerId )
 {
     const auto it = m_data->hashTab.find( qskKey( providerId ) );
-    if ( it == m_data->hashTab.constEnd() )
+    if ( it == m_data->hashTab.end() )
         delete it.value();
 
     m_data->hashTab.erase( it );
@@ -61,7 +61,7 @@ QskGraphicProvider* QskGraphicProviderMap::take( const QString& providerId )
     QskGraphicProvider* provider = nullptr;
 
     const auto it = m_data->hashTab.find( qskKey( providerId ) );
-    if ( it == m_data->hashTab.constEnd() )
+    if ( it == m_data->hashTab.end() )
         provider = it.value();
 
     m_data->hashTab.erase( it );
@@ -72,7 +72,7 @@ QskGraphicProvider* QskGraphicProviderMap::take( const QString& providerId )
 QskGraphicProvider* QskGraphicProviderMap::provider( const QString& providerId ) const
 {
     const auto it = m_data->hashTab.find( qskKey( providerId ) );
-    if ( it == m_data->hashTab.constEnd() )
+    if ( it == m_data->hashTab.end() )
         return nullptr;
 
     if ( it.value().isNull() )