diff --git a/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.rst b/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.rst
index 03080fec50..8a4f25cc2b 100644
--- a/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.rst
+++ b/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.rst
@@ -90,7 +90,7 @@ This tutorial code's is shown lines below. You can also download it from `here <
     //-- Detect faces
     face_cascade.detectMultiScale( frame_gray, faces, 1.1, 2, 0|CV_HAAR_SCALE_IMAGE, Size(30, 30) );
 
-    for( int i = 0; i < faces.size(); i++ )
+    for( size_t i = 0; i < faces.size(); i++ )
     {
       Point center( faces[i].x + faces[i].width*0.5, faces[i].y + faces[i].height*0.5 );
       ellipse( frame, center, Size( faces[i].width*0.5, faces[i].height*0.5), 0, 0, 360, Scalar( 255, 0, 255 ), 4, 8, 0 );
@@ -101,7 +101,7 @@ This tutorial code's is shown lines below. You can also download it from `here <
       //-- In each face, detect eyes
       eyes_cascade.detectMultiScale( faceROI, eyes, 1.1, 2, 0 |CV_HAAR_SCALE_IMAGE, Size(30, 30) );
 
-      for( int j = 0; j < eyes.size(); j++ )
+      for( size_t j = 0; j < eyes.size(); j++ )
        {
          Point center( faces[i].x + eyes[j].x + eyes[j].width*0.5, faces[i].y + eyes[j].y + eyes[j].height*0.5 );
          int radius = cvRound( (eyes[j].width + eyes[j].height)*0.25 );