Index: src/test/org/apache/lucene/analysis/TestAnalyzers.java
===================================================================
--- src/test/org/apache/lucene/analysis/TestAnalyzers.java	(revision 596776)
+++ src/test/org/apache/lucene/analysis/TestAnalyzers.java	(working copy)
@@ -118,6 +118,29 @@
     verifyPayload(ts);
   }
 
+  // Make sure that tokenizers that define the non-reuse
+  // next() API do not see their returned tokens changed by
+  // subsequent filters that use the re-use next(Token) API:
+  public void testTokenReuse() throws IOException {
+    TokenStream source = new TokenStream() {
+
+      private Token theToken;
+
+      // TokenStream that just returns one token "A"
+      public Token next() {
+        if (theToken == null)
+          theToken = new Token("A", 0, 3);
+        char[] termBuffer = theToken.termBuffer();
+        assertEquals('A', termBuffer[0]);
+        return theToken;
+      }
+    };
+
+    TokenStream filtered = new LowerCaseFilter(source);
+    
+    filtered.next();
+    filtered.next();
+  }
 }
 
 class BuffTokenFilter extends TokenFilter {
Index: src/java/org/apache/lucene/analysis/Token.java
===================================================================
--- src/java/org/apache/lucene/analysis/Token.java	(revision 596776)
+++ src/java/org/apache/lucene/analysis/Token.java	(working copy)
@@ -386,4 +386,19 @@
       throw new RuntimeException(e);  // shouldn't happen
     }
   }
+
+  /** Make a full copy of this token into the destination
+   *  token, and return the destination token. */
+  Token copyTo(Token dest) {
+    initTermBuffer();
+    dest.setTermBuffer(termBuffer, 0, termLength);
+    dest.startOffset = startOffset;
+    dest.endOffset = endOffset;
+    dest.type = type;
+    dest.payload = payload;
+    dest.positionIncrement = positionIncrement;
+    if (payload != null)
+      dest.setPayload(new Payload(payload.toByteArray(), 0, payload.length()));
+    return dest;
+  }
 }
Index: src/java/org/apache/lucene/analysis/TokenStream.java
===================================================================
--- src/java/org/apache/lucene/analysis/TokenStream.java	(revision 596776)
+++ src/java/org/apache/lucene/analysis/TokenStream.java	(working copy)
@@ -38,9 +38,11 @@
 public abstract class TokenStream {
 
   /** Returns the next token in the stream, or null at EOS.
-   *  The returned Token is a "full private copy" (not
-   *  re-used across calls to next()) but will be slower
-   *  than calling {@link #next(Token)} instead.. */
+   *  The returned Token is safe to store away indefinitely
+   *  (will not be changed on future calls to next), and you
+   *  must not alter any of the fields in the Token.  This
+   *  is in general slower than calling {@link
+   *  #next(Token)}. */
   public Token next() throws IOException {
     Token result = next(new Token());
 
@@ -56,17 +58,24 @@
   /** Returns the next token in the stream, or null at EOS.
    *  When possible, the input Token should be used as the
    *  returned Token (this gives fastest tokenization
-   *  performance), but this is not required and a new Token
-   *  may be returned.  Callers may re-use a single Token
-   *  instance for successive calls to this method and must
-   *  therefore fully consume the previously returned Token
-   *  before calling this method again.
+   *  performance) but this is not required.  Callers may
+   *  re-use a single Token instance for successive calls to
+   *  this method and must therefore fully consume the
+   *  previously returned Token before calling this method
+   *  again.  Furthermore, it is OK to modify the fields in
+   *  the returned Token.
    *  @param result a Token that may or may not be used to
    *   return
    *  @return next token in the stream or null if
    *   end-of-stream was hit*/
   public Token next(Token result) throws IOException {
-    return next();
+    Token t = next();
+    if (t == null)
+      return null;
+    else
+      // We must make a copy here because our caller is
+      // allowed to modify the fields in the returned token
+      return t.copyTo(result);
   }
 
   /** Resets this stream to the beginning. This is an