diff --git a/core/sample-vpImageConvert-6.cpp b/core/sample-vpImageConvert-6.cpp
index d1806c5..9212180 100644
--- a/core/sample-vpImageConvert-6.cpp
+++ b/core/sample-vpImageConvert-6.cpp
@@ -2,6 +2,10 @@
 #include <visp3/core/vpImageConvert.h>
 #include <visp3/io/vpImageIo.h>
 
+#if defined(HAVE_OPENCV_IMGCODECS)
+#include <opencv2/imgcodecs.hpp>
+#endif
+
 int main()
 {
 #if defined(VISP_HAVE_OPENCV) && defined(HAVE_OPENCV_IMGPROC) && defined(HAVE_OPENCV_IMGCODECS)
diff --git a/core/sample-vpImageConvert-8.cpp b/core/sample-vpImageConvert-8.cpp
index 7d505ff..9159fd1 100644
--- a/core/sample-vpImageConvert-8.cpp
+++ b/core/sample-vpImageConvert-8.cpp
@@ -2,6 +2,10 @@
 #include <visp3/core/vpImageConvert.h>
 #include <visp3/io/vpImageIo.h>
 
+#if defined(HAVE_OPENCV_IMGCODECS)
+#include <opencv2/imgcodecs.hpp>
+#endif
+
 int main()
 {
 #if defined(VISP_HAVE_OPENCV) && defined(HAVE_OPENCV_IMGPROC) && defined(HAVE_OPENCV_IMGCODECS)
diff --git a/core/sample-vpImageConvert-9.cpp b/core/sample-vpImageConvert-9.cpp
index 829278a..195e584 100644
--- a/core/sample-vpImageConvert-9.cpp
+++ b/core/sample-vpImageConvert-9.cpp
@@ -2,6 +2,11 @@
 #include <visp3/core/vpImageConvert.h>
 #include <visp3/io/vpImageIo.h>
 
+
+#if defined(HAVE_OPENCV_IMGCODECS)
+#include <opencv2/imgcodecs.hpp>
+#endif
+
 int main()
 {
 #if defined(VISP_HAVE_OPENCV) && defined(HAVE_OPENCV_IMGPROC) && defined(HAVE_OPENCV_IMGCODECS)