diff --git a/modules/highgui/include/opencv2/highgui/highgui.hpp b/modules/highgui/include/opencv2/highgui/highgui.hpp
index 6468568c9a8a15f3c7cbd48bcc28e2e0d4a51c67..b6dbb3c01eb07ddb5b4a4eb12c67bce9ebe44da1 100644
--- a/modules/highgui/include/opencv2/highgui/highgui.hpp
+++ b/modules/highgui/include/opencv2/highgui/highgui.hpp
@@ -156,7 +156,7 @@ CV_EXPORTS_W bool imwrite( const string& filename, InputArray img,
               const vector<int>& params=vector<int>());
 CV_EXPORTS_W Mat imdecode( InputArray buf, int flags );
 CV_EXPORTS_W bool imencode( const string& ext, InputArray img,
-                            vector<uchar>& buf,
+                            CV_OUT vector<uchar>& buf,
                             const vector<int>& params=vector<int>());
 
 CV_EXPORTS_W int waitKey(int delay=0);