diff --git a/modules/ml/src/gbt.cpp b/modules/ml/src/gbt.cpp
index b186abf672..0ebe19ea30 100644
--- a/modules/ml/src/gbt.cpp
+++ b/modules/ml/src/gbt.cpp
@@ -268,6 +268,7 @@ CvGBTrees::train( const CvMat* _train_data, int _tflag,
                 sample_idx = cvCreateMat( 1, sample_idx_len, CV_32S );
                 for (int i=0; i<sample_idx_len; ++i)
                     sample_idx->data.i[i] = _sample_idx->data.i[i];
+                std::sort(sample_idx->data.i, sample_idx->data.i + sample_idx_len);
             } break;
             case CV_8S:
             case CV_8U:
@@ -284,7 +285,6 @@ CvGBTrees::train( const CvMat* _train_data, int _tflag,
             } break;
             default: CV_Error(CV_StsUnmatchedFormats, "_sample_idx should be a 32sC1, 8sC1 or 8uC1 vector.");
         }
-        std::sort(sample_idx->data.fl, sample_idx->data.fl + sample_idx_len);
     }
     else
     {