diff --git a/.github/workflows/create_releases.yaml b/.github/workflows/create_releases.yaml
index e35b068..53528f8 100644
--- a/.github/workflows/create_releases.yaml
+++ b/.github/workflows/create_releases.yaml
@@ -53,7 +53,7 @@ jobs:
       - name: Install Qt
         uses: jurplel/install-qt-action@v3
         with:
-          version: "6.10.2"
+          version: "5.15.2" # "6.10.2"
           host: "linux"
 
       - name: Install GDAL
diff --git a/.github/workflows/test_library.yaml b/.github/workflows/test_library.yaml
index 9c9e9fa..22224fe 100644
--- a/.github/workflows/test_library.yaml
+++ b/.github/workflows/test_library.yaml
@@ -141,7 +141,7 @@ jobs:
       - name: Install Qt
         uses: jurplel/install-qt-action@v3
         with:
-          version: "6.10.2"
+          version: "5.15.2" #"6.10.2"
           host: "linux"
 
       - name: Configure
diff --git a/CMakeLists.txt b/CMakeLists.txt
index bbd1398..00a6149 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -34,19 +34,24 @@ find_package(SimpleRasters REQUIRED)
 if(NEEDS_QT)
     set(CMAKE_AUTOMOC TRUE)
 
-    find_package(Qt6 COMPONENTS Core Xml Test REQUIRED)
+    find_package(Qt5 COMPONENTS Core Xml Test REQUIRED)
+    # find_package(Qt6 COMPONENTS Core Xml Test REQUIRED)
 
     set(QT_LIBS
-        Qt6::Core
+        Qt5::Core
+        # Qt6::Core
     )
 
     if(BUILD_GUI_APP)
-        find_package(Qt6 COMPONENTS Core Widgets Xml Gui Test REQUIRED)
+        find_package(Qt5 COMPONENTS Core Widgets Xml Gui Test REQUIRED)
+        # find_package(Qt6 COMPONENTS Core Widgets Xml Gui Test REQUIRED)
 
         set(QT_LIBS
             ${QT_LIBS}
-            Qt6::Gui
-            Qt6::Widgets
+            Qt5::Gui
+            Qt5::Widgets
+            # Qt6::Gui
+            # Qt6::Widgets
         )
     endif()
 
diff --git a/conda/meta.yaml b/conda/meta.yaml
index 2bddbc5..539782e 100644
--- a/conda/meta.yaml
+++ b/conda/meta.yaml
@@ -15,18 +15,18 @@ requirements:
     - pthread-stubs
     - libgdal
     - libsimplerasters
-    - qt-main 6.*
+    - qt-main 5.*
     - mesalib # [unix]
   host:
     - pthread-stubs
     - libgdal
     - libsimplerasters
-    - qt-main 6.*
+    - qt-main 5.*
     - mesalib # [unix]
   run:
     - libgdal
     - libsimplerasters
-    - qt-main 6.*
+    - qt-main 5.*
     - mesalib # [unix]
 
 test:
diff --git a/src/bin/losextractor.cpp b/src/bin/losextractor.cpp
index a635376..bb8b3a5 100644
--- a/src/bin/losextractor.cpp
+++ b/src/bin/losextractor.cpp
@@ -232,7 +232,11 @@ namespace ViewshedBinaries
             connect( mFileWidget, &FileSelectorWidget::fileChanged, this, &MainWindow::demUpdated );
             connect( mCsvFileWidget, &FileSelectorWidget::fileChanged, this, &MainWindow::updateResultCsv );
             connect( mCalculateButton, &QPushButton::clicked, this, &MainWindow::calculateViewshed );
-            connect( mCurvatureCorrections, &QCheckBox::checkStateChanged, this, &MainWindow::saveSettings );
+
+            // Qt 6
+            // connect( mCurvatureCorrections, &QCheckBox::checkStateChanged, this, &MainWindow::saveSettings );
+            connect( mCurvatureCorrections, &QCheckBox::stateChanged, this, &MainWindow::saveSettings );
+
             connect( mRefractionCoefficient, &QLineEdit::textChanged, this, &MainWindow::saveSettings );
             connect( mEarthDiameter, &QLineEdit::textChanged, this, &MainWindow::saveSettings );
 
diff --git a/src/bin/viewshedcalculatorwindow.cpp b/src/bin/viewshedcalculatorwindow.cpp
index 3df8f9f..3cfe2f9 100644
--- a/src/bin/viewshedcalculatorwindow.cpp
+++ b/src/bin/viewshedcalculatorwindow.cpp
@@ -202,8 +202,12 @@ void MainCalculatorWindow::initGui()
 
     connect( mViewshedType, qOverload<int>( &QComboBox::currentIndexChanged ), this,
              &MainCalculatorWindow::saveSettings );
-    connect( mNoDataForInvisible, &QCheckBox::checkStateChanged, this, &MainCalculatorWindow::saveSettings );
-    connect( mCurvatureCorrections, &QCheckBox::checkStateChanged, this, &MainCalculatorWindow::saveSettings );
+    // Qt 6
+    // connect( mNoDataForInvisible, &QCheckBox::checkStateChanged, this, &MainCalculatorWindow::saveSettings );
+    // connect( mCurvatureCorrections, &QCheckBox::checkStateChanged, this, &MainCalculatorWindow::saveSettings );
+    connect( mNoDataForInvisible, &QCheckBox::stateChanged, this, &MainCalculatorWindow::saveSettings );
+    connect( mCurvatureCorrections, &QCheckBox::stateChanged, this, &MainCalculatorWindow::saveSettings );
+
     connect( mRefractionCoefficient, &QLineEdit::textChanged, this, &MainCalculatorWindow::saveSettings );
     connect( mEarthDiameter, &QLineEdit::textChanged, this, &MainCalculatorWindow::saveSettings );
     connect( mFileWidget, &FileSelectorWidget::fileChanged, this, &MainCalculatorWindow::validateDem );
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 81a0c7f..494ac90 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -53,7 +53,8 @@ macro(add_gui_test filename)
         GDAL::GDAL
         SimpleRasters::simplerasters_shared
         ${QT_LIBS}
-        Qt6::Test
+        Qt5::Test
+        # Qt6::Test
         viewshed_widgets
     )