diff --git a/include/deltille/DetectorTools.h b/include/deltille/DetectorTools.h
index fe6c9bb..70fb503 100644
--- a/include/deltille/DetectorTools.h
+++ b/include/deltille/DetectorTools.h
@@ -186,7 +186,7 @@ void stretchIntensities(cv::InputArray input, cv::OutputArray output);
 template <typename FloatPoint>
 void subpixel_marker(cv::Mat &img, const FloatPoint &pt, float sz,
                      const cv::Scalar &color, int thickness = 1,
-                     int lineType = CV_AA) {
+                     int lineType = cv::LINE_AA) {
   const int shift = 16;
   const float ss = (1 << shift);
   cv::rectangle(img, cv::Point(int((pt.x - sz) * ss), int((pt.y - sz) * ss)),
@@ -197,7 +197,7 @@ void subpixel_marker(cv::Mat &img, const FloatPoint &pt, float sz,
 template <typename FloatPoint>
 void subpixel_line(cv::Mat &img, const FloatPoint &pt1, const FloatPoint &pt2,
                    const cv::Scalar &color, int thickness = 1,
-                   int lineType = CV_AA) {
+                   int lineType = cv::LINE_AA) {
   const int shift = 16;
   const float ss = (1 << shift);
   cv::line(img, cv::Point(int(pt1.x * ss), int(pt1.y * ss)),
diff --git a/include/deltille/PolynomialSaddleDetectorContext.h b/include/deltille/PolynomialSaddleDetectorContext.h
index d5e6043..d618db1 100644
--- a/include/deltille/PolynomialSaddleDetectorContext.h
+++ b/include/deltille/PolynomialSaddleDetectorContext.h
@@ -255,7 +255,7 @@ struct PolynomialSaddleDetectorContext {
     if (img.getMat().channels() == 3)
       // convert to a single channel first, keep original intensity range for
       // now...
-      cvtColor(img, gray_img, CV_RGB2GRAY);
+      cvtColor(img, gray_img, cv::COLOR_RGB2GRAY);
     else
       gray_img = img.getMat();
 
diff --git a/include/deltille/target_detector.h b/include/deltille/target_detector.h
index b50cb2f..ad3c770 100644
--- a/include/deltille/target_detector.h
+++ b/include/deltille/target_detector.h
@@ -91,7 +91,7 @@ FindBoards(const cv::Mat &I, const cv::Size &board_size,
   case cv::DataType<uint16_t>::type:
     return FindBoardsHelper<SaddlePointType, FloatImageType, uint16_t>(
         I, board_size, boards);
-  case cv::DataType<uint32_t>::type:
+  case cv::DataType<int32_t>::type:
     return FindBoardsHelper<SaddlePointType, FloatImageType, uint32_t>(
         I, board_size, boards);
   case cv::DataType<float>::type:
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 800b579..9de892b 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -14,7 +14,7 @@
 ## License along with this library; if not, write to the Free Software
 ## Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 
-find_package(OpenCV 3 CONFIG REQUIRED COMPONENTS core highgui imgproc imgcodecs) 
+find_package(OpenCV 4 CONFIG REQUIRED COMPONENTS core highgui imgproc imgcodecs) 
 add_library(opencv INTERFACE IMPORTED)
 set_target_properties(opencv PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES "${OpenCV_INCLUDE_DIRS}"