diff --git a/lucene/src/test/org/apache/lucene/index/TestIndexWriterOnDiskFull.java b/lucene/src/test/org/apache/lucene/index/TestIndexWriterOnDiskFull.java
index 4a7eb3b7f92..2729b949106 100644
--- a/lucene/src/test/org/apache/lucene/index/TestIndexWriterOnDiskFull.java
+++ b/lucene/src/test/org/apache/lucene/index/TestIndexWriterOnDiskFull.java
@@ -20,6 +20,7 @@ package org.apache.lucene.index;
 import java.io.IOException;
 
 import org.apache.lucene.analysis.MockAnalyzer;
+import org.apache.lucene.codecs.LiveDocsFormat;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.FieldType;
 import org.apache.lucene.document.TextField;
@@ -453,13 +454,13 @@ public class TestIndexWriterOnDiskFull extends LuceneTestCase {
       }
       StackTraceElement[] trace = new Exception().getStackTrace();
       for (int i = 0; i < trace.length; i++) {
-        if ("org.apache.lucene.index.SegmentMerger".equals(trace[i].getClassName()) && "mergeTerms".equals(trace[i].getMethodName()) && !didFail1) {
+        if (SegmentMerger.class.getName().equals(trace[i].getClassName()) && "mergeTerms".equals(trace[i].getMethodName()) && !didFail1) {
           didFail1 = true;
           throw new IOException("fake disk full during mergeTerms");
         }
-        if ("org.apache.lucene.util.BitVector".equals(trace[i].getClassName()) && "write".equals(trace[i].getMethodName()) && !didFail2) {
+        if (LiveDocsFormat.class.getName().equals(trace[i].getClassName()) && "writeLiveDocs".equals(trace[i].getMethodName()) && !didFail2) {
           didFail2 = true;
-          throw new IOException("fake disk full while writing BitVector");
+          throw new IOException("fake disk full while writing LiveDocs");
         }
       }
     }