diff --git a/samples/cpp/bagofwords_classification.cpp b/samples/cpp/bagofwords_classification.cpp
index 7203ccc5a..8226dc3c5 100644
--- a/samples/cpp/bagofwords_classification.cpp
+++ b/samples/cpp/bagofwords_classification.cpp
@@ -1860,7 +1860,7 @@ string VocData::checkFilenamePathsep( const string filename, bool add_trailing_s
     pos = filename_new.find("\\");
     while (pos != filename_new.npos)
     {
-        filename_new.replace(pos,2,"/");
+        filename_new.replace(pos,1,"/");
         pos = filename_new.find("\\", pos);
     }
     if (add_trailing_slash)