Index: lucene/src/java/org/apache/lucene/index/codecs/preflex/PreFlexFields.java
===================================================================
--- lucene/src/java/org/apache/lucene/index/codecs/preflex/PreFlexFields.java	(revision 957636)
+++ lucene/src/java/org/apache/lucene/index/codecs/preflex/PreFlexFields.java	(working copy)
@@ -319,7 +319,8 @@
           assert pendingPrefix != null;
           assert pendingPrefix.length > seekPrefix;
           pendingPrefix[seekPrefix] = UnicodeUtil.UNI_SUR_HIGH_START;
-          Term t2 = protoTerm.createTerm(new String(pendingPrefix, 0, 1+seekPrefix));
+          pendingPrefix[1+seekPrefix] = UnicodeUtil.UNI_SUR_LOW_START;
+          Term t2 = protoTerm.createTerm(new String(pendingPrefix, 0, 2+seekPrefix));
           if (DEBUG_SURROGATES) {
             System.out.println("    do pop; seek back to " + UnicodeUtil.toHexString(t2.text()));
           }
@@ -385,13 +386,13 @@
           // surrogate range; if so, we must first iterate
           // them, then seek back to the surrogates
 
-          char[] testPrefix = new char[i+1];
+          char[] testPrefix = new char[i+2];
           for(int j=0;j<i;j++) {
             testPrefix[j] = text.charAt(j);
           }
           testPrefix[i] = 1+UnicodeUtil.UNI_SUR_LOW_END;
 
-          getTermsDict().seekEnum(seekTermEnum, protoTerm.createTerm(new String(testPrefix)));
+          getTermsDict().seekEnum(seekTermEnum, protoTerm.createTerm(new String(testPrefix, 0, i+1)));
 
           Term t2 = seekTermEnum.term();
           boolean isPrefix;