Index: src/org/openstreetmap/josm/gui/tagging/ac/MaxLengthDocumentFilter.java
===================================================================
--- src/org/openstreetmap/josm/gui/tagging/ac/MaxLengthDocumentFilter.java	(revision 18233)
+++ src/org/openstreetmap/josm/gui/tagging/ac/MaxLengthDocumentFilter.java	(working copy)
@@ -1,6 +1,8 @@
 // License: GPL. For details, see LICENSE file.
 package org.openstreetmap.josm.gui.tagging.ac;
 
+import static org.openstreetmap.josm.tools.I18n.tr;
+
 import javax.swing.text.AttributeSet;
 import javax.swing.text.BadLocationException;
 import javax.swing.text.DocumentFilter;
@@ -13,6 +15,7 @@
 public class MaxLengthDocumentFilter extends DocumentFilter {
     /** the document will not accept text longer than this. -1 to disable */
     private int maxLength = -1;
+    private static final String DIFFERENT = tr("<different>");
 
     /**
      * Sets the maximum text length.
@@ -41,7 +44,7 @@
 
     private boolean mustInsertOrReplace(FilterBypass fb, int length, String string, AttributeSet attr) {
         int newLen = fb.getDocument().getLength() - length + ((string == null) ? 0 : string.length());
-        return (maxLength == -1 || newLen <= maxLength ||
+        return (maxLength == -1 || newLen <= maxLength || DIFFERENT.equals(string) ||
                 // allow longer text while composing characters or it will be hard to compose
                 // the last characters before the limit
                 ((attr != null) && attr.isDefined(StyleConstants.ComposedTextAttribute)));