[Koha] string completion problem

hello , i have problem in string completion the search always make string completion, and i want to stop this feature , if i search for specific word , it returns the words that this word is part of . for eaxmble , if i search for the word "exact" it return "exactly" i used this page http://www.indexdata.com/zebra/doc/querymodel-rpn.html#querymodel-bib1-trunc... and change the values in zebradb/ccl.properties file in line 868 in (startswithnt ) but there is no change can you help me thank you