An error when saving the vocabulary to disk

[jsdd25]

When I ran demo, there was an error occurred. Here is part of the output:
"OpenCV Error: Bad argument (The written string is too long) in icvYMLWriteString, file /home/jin/opencv-3.2.0/modules/core/src/persistence.cpp, line 2111
terminate called after throwing an instance of 'cv::Exception'
what(): /home/jin/opencv-3.2.0/modules/core/src/persistence.cpp:2111: error: (-5) The written string is too long in function icvYMLWriteString".
How should I solve it? Thank you very much!