Index: src/java/org/apache/lucene/analysis/CharArraySet.java
===================================================================
--- src/java/org/apache/lucene/analysis/CharArraySet.java	(revision 883650)
+++ src/java/org/apache/lucene/analysis/CharArraySet.java	(working copy)
@@ -131,8 +131,15 @@
    */
   public boolean add(char[] text) {
     if (ignoreCase)
-      for(int i=0;i<text.length;i++)
-        text[i] = Character.toLowerCase(text[i]);
+      for(int i=0;i<text.length;i++){
+        if(Character.isHighSurrogate(text[i])){
+          final int codePointAt = Character.codePointAt(text, i);
+          i += Character.toChars(Character.toLowerCase(codePointAt),
+              text, i)-1;
+        } else {
+          text[i] = Character.toLowerCase(text[i]);
+        }
+      }
     int slot = getSlot(text, 0, text.length);
     if (entries[slot] != null) return false;
     entries[slot] = text;
@@ -150,8 +157,12 @@
       return false;
     if (ignoreCase) {
       for(int i=0;i<len;i++) {
-        if (Character.toLowerCase(text1[off+i]) != text2[i])
+        final int codePointAt = Character.codePointAt(text1, off+i);
+        if (Character.toLowerCase(codePointAt) != Character.codePointAt(text2, i))
           return false;
+        if(codePointAt >= Character.MIN_SUPPLEMENTARY_CODE_POINT){
+          ++i;
+         }
       }
     } else {
       for(int i=0;i<len;i++) {
@@ -168,8 +179,12 @@
       return false;
     if (ignoreCase) {
       for(int i=0;i<len;i++) {
-        if (Character.toLowerCase(text1.charAt(i)) != text2[i])
+        final int codePointAt = Character.codePointAt(text1, i);
+        if (Character.toLowerCase(codePointAt) != Character.codePointAt(text2, i))
           return false;
+        if(codePointAt >= Character.MIN_SUPPLEMENTARY_CODE_POINT){
+          ++i;
+         }
       }
     } else {
       for(int i=0;i<len;i++) {
@@ -179,7 +194,9 @@
     }
     return true;
   }
+  
 
+
   private void rehash() {
     final int newSize = 2*entries.length;
     char[][] oldEntries = entries;
@@ -199,7 +216,11 @@
     final int stop = offset + len;
     if (ignoreCase) {
       for (int i=offset; i<stop; i++) {
-        code = code*31 + Character.toLowerCase(text[i]);
+        final int codePointAt = Character.codePointAt(text, i);
+        code = code*31 + Character.toLowerCase(codePointAt);
+        if(codePointAt >= Character.MIN_SUPPLEMENTARY_CODE_POINT){
+          ++i;
+         }
       }
     } else {
       for (int i=offset; i<stop; i++) {
@@ -214,7 +235,11 @@
     int len = text.length();
     if (ignoreCase) {
       for (int i=0; i<len; i++) {
-        code = code*31 + Character.toLowerCase(text.charAt(i));
+        int codePointAt = Character.codePointAt(text, i);
+        code = code*31 + Character.toLowerCase(codePointAt);
+        if(codePointAt >= Character.MIN_SUPPLEMENTARY_CODE_POINT){
+         ++i;
+        }
       }
     } else {
       for (int i=0; i<len; i++) {
Index: src/test/org/apache/lucene/analysis/TestCharArraySet.java
===================================================================
--- src/test/org/apache/lucene/analysis/TestCharArraySet.java	(revision 883650)
+++ src/test/org/apache/lucene/analysis/TestCharArraySet.java	(working copy)
@@ -175,4 +175,18 @@
       // expected
     }
   }
+  
+  public void testHighSurrogateChars(){
+    String upper = "Abc𐐜";
+    String lower = "abc𐑄";
+    CharArraySet set = new CharArraySet(Arrays.asList(TEST_STOP_WORDS), true);
+    set.add(upper);
+    assertTrue(set.contains(lower));
+    assertTrue(set.contains(upper));
+    
+    set = new CharArraySet(Arrays.asList(TEST_STOP_WORDS), false);
+    set.add(upper);
+    assertFalse(set.contains(lower));
+    assertTrue(set.contains(upper));
+  }
 }