Index: modules/analysis/common/src/java/org/apache/lucene/analysis/en/KStemFilter.java
===================================================================
--- modules/analysis/common/src/java/org/apache/lucene/analysis/en/KStemFilter.java	(revision 1134263)
+++ modules/analysis/common/src/java/org/apache/lucene/analysis/en/KStemFilter.java	(working copy)
@@ -55,8 +55,11 @@
     char[] term = termAttribute.buffer();
     int len = termAttribute.length();
     if ((!keywordAtt.isKeyword()) && stemmer.stem(term, len)) {
-      char[] chars = stemmer.asString().toCharArray();
-      termAttribute.copyBuffer(chars, 0, chars.length);
+      String result = stemmer.asString();
+      int stemLen = result.length();
+      termAttribute.resizeBuffer(stemLen);
+      termAttribute.setLength(stemLen);
+      result.getChars(0, stemLen, termAttribute.buffer(), 0);
     }
 
     return true;