Index: src/main/java/org/apache/jackrabbit/core/version/InternalVersionHistoryImpl.java
===================================================================
--- src/main/java/org/apache/jackrabbit/core/version/InternalVersionHistoryImpl.java	(revision 1421808)
+++ src/main/java/org/apache/jackrabbit/core/version/InternalVersionHistoryImpl.java	(working copy)
@@ -18,6 +18,7 @@
 
 import java.util.Calendar;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -167,7 +168,7 @@
     // fix legacy
     private void fixLegacy() throws RepositoryException {
         if (rootVersion.getSuccessors().isEmpty()) {
-            for (Name versionName : nameCache.keySet()) {
+            for (Name versionName : new HashSet<Name>(nameCache.keySet())) {
                 InternalVersionImpl v = createVersionInstance(versionName);
                 v.legacyResolveSuccessors();
             }