diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 354b224f..7b5a0f18 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,35 +8,35 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest]
+        qtver: [5.12.12, 6.5.3]
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
-
-      - name: Cache Qt
-        id: cache-qt
-        uses: actions/cache@v2
-        with:
-          path: ${{ github.workspace }}/Qt/
-          key: ${{ runner.os }}-QtCache-5-12-12
+        uses: actions/checkout@v4
 
       - name: Install Qt
-        uses: jurplel/install-qt-action@v2
+        uses: jurplel/install-qt-action@v3
         with:
-          version: 5.12.12
+          version: ${{ matrix.qtver }}
           dir: "${{ github.workspace }}/Qt/"
-          cached: ${{ steps.cache-qt.outputs.cache-hit }}
+          cache: true
+          cache-key-prefix: ${{ matrix.qtver }}-${{ matrix.os }}
 
       - name: Install Linux dependencies
         if: "contains( matrix.os, 'ubuntu')"
         run: sudo apt-get install libxkbcommon-x11-0 libgl1-mesa-dev mesa-common-dev libglfw3-dev libglu1-mesa-dev
+      
+      - name: Use MSVC (Windows)
+        uses: ilammy/msvc-dev-cmd@v1
 
-      - name: Build 
-        uses: lukka/run-cmake@v1
-        with:
-          cmakeListsOrSettingsJson: CMakeListsTxtAdvanced
-          cmakeListsTxtPath: "${{ github.workspace }}/CMakeLists.txt"
-          cmakeAppendedArgs:
-          buildDirectory: ${{ github.workspace }}/cmakebuild
-          buildWithCMakeArgs: "--config Release"
-          useVcpkgToolchainFile: false
- 
+      - name: Configure 5.12
+        if: "contains( matrix.qtver, '5.12')"
+        run: |
+          cmake -S . -B build
+
+      - name: Configure 6.5
+        if: "contains( matrix.qtver, '6.5')"
+        run: |
+          cmake -S . -DUSE_QT6=TRUE -B build
+  
+      - name: Build
+        run: cmake --build build
diff --git a/.gitignore b/.gitignore
index dff97119..832aaace 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,3 +10,4 @@ plugins
 resources
 Doxygen.log
 *.swp
+build
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a0ffc249..9f1e10a0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.15)
 
 project(qwt)
 
@@ -15,8 +15,16 @@ add_definitions(-DQWT_NO_SVG -DQWT_MOC_INCLUDE)
 
 include(src/CMakeLists.txt)
 
-find_package(Qt5 COMPONENTS REQUIRED Concurrent Core Gui OpenGL PrintSupport Widgets)
-set(QT_LIBRARIES Qt5::Concurrent Qt5::Core Qt5::Gui Qt5::OpenGL Qt5::PrintSupport Qt5::Widgets)
+option(USE_QT6 "Use Qt6" FALSE)
+
+if(USE_QT6)
+  find_package(Qt6 COMPONENTS REQUIRED Concurrent Core Gui OpenGLWidgets PrintSupport Widgets)
+  set(QT_LIBRARIES Qt6::Concurrent Qt6::Core Qt6::Gui Qt6::OpenGLWidgets Qt6::PrintSupport Qt6::Widgets)
+else(USE_QT6)
+  find_package(Qt5 COMPONENTS REQUIRED Concurrent Core Gui OpenGL PrintSupport Widgets)
+  set(QT_LIBRARIES Qt5::Concurrent Qt5::Core Qt5::Gui Qt5::OpenGL Qt5::PrintSupport Qt5::Widgets)
+endif(USE_QT6)
+
 
 set(CMAKE_AUTOMOC ON)
 add_library(${PROJECT_NAME} src/CMakeLists.txt ${HEADER_FILES} ${SOURCE_FILES} )
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 04b08b61..d0dbbfd8 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,5 +1,3 @@
-cmake_minimum_required(VERSION 2.8.12)
-
 set(HEADER_FILES ${HEADER_FILES}
 src/qwt.h 
 src/qwt_abstract_scale_draw.h 
@@ -207,12 +205,10 @@ src/qwt_scale_widget.cpp)
 
 # QwtOpenGL
 set(HEADER_FILES ${HEADER_FILES}
-src/qwt_plot_glcanvas.h
 src/qwt_plot_opengl_canvas.h
 )
 
 set(SOURCE_FILES ${SOURCE_FILES}
-src/qwt_plot_glcanvas.cpp
 src/qwt_plot_opengl_canvas.cpp
 )