diff --git a/source/java/org/alfresco/repo/avm/AVMServiceTest.java b/source/java/org/alfresco/repo/avm/AVMServiceTest.java
index 6fe2d05006..78d0a22957 100644
--- a/source/java/org/alfresco/repo/avm/AVMServiceTest.java
+++ b/source/java/org/alfresco/repo/avm/AVMServiceTest.java
@@ -59,6 +59,42 @@ import org.alfresco.service.transaction.TransactionService;
  */
 public class AVMServiceTest extends AVMServiceTestBase
 {
+    /**
+     * Test that non head version sources are update correctly.
+     */
+    public void testVersionUpdate()
+    {
+        try
+        {
+            BulkLoader loader = new BulkLoader();
+            loader.setAvmService(fService);
+            fService.createAVMStore("source");
+            fService.createAVMStore("dest");
+            loader.recursiveLoad("config/alfresco/bootstrap", "source:/");
+            int version1 = fService.createSnapshot("source");
+            loader.recursiveLoad("config/alfresco/extension", "source:/");
+            int version2 = fService.createSnapshot("source");
+            List<AVMDifference> diffs = 
+                fSyncService.compare(version1, "source:/", -1, "dest:/");
+            fService.createSnapshot("dest");
+            assertEquals(1, diffs.size());
+            fSyncService.update(diffs, false, false, false, false);
+            diffs = fSyncService.compare(version1, "source:/", -1, "dest:/");
+            assertEquals(0, diffs.size());
+            diffs = fSyncService.compare(version2, "source:/", -1, "dest:/");
+            assertEquals(1, diffs.size());
+            fSyncService.update(diffs, false, false, false, false);
+            fService.createSnapshot("dest");
+            diffs = fSyncService.compare(version2, "source:/", -1, "dest:/");
+            assertEquals(0, diffs.size());
+        }
+        catch (Exception e)
+        {
+            e.printStackTrace(System.err);
+            fail();
+        }
+    }
+    
     /**
      * Test that an update forces a snapshot on the source.
      */
diff --git a/source/java/org/alfresco/repo/avm/AVMSyncServiceImpl.java b/source/java/org/alfresco/repo/avm/AVMSyncServiceImpl.java
index 84a095cf23..b7f9e73b82 100644
--- a/source/java/org/alfresco/repo/avm/AVMSyncServiceImpl.java
+++ b/source/java/org/alfresco/repo/avm/AVMSyncServiceImpl.java
@@ -18,8 +18,11 @@
 package org.alfresco.repo.avm;
 
 import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import org.alfresco.service.cmr.avm.AVMBadArgumentException;
 import org.alfresco.service.cmr.avm.AVMNodeDescriptor;
@@ -281,19 +284,33 @@ public class AVMSyncServiceImpl implements AVMSyncService
     public void update(List<AVMDifference> diffList, boolean ignoreConflicts, boolean ignoreOlder,
                        boolean overrideConflicts, boolean overrideOlder)
     {
+        Map<String, Integer> storeVersions = new HashMap<String, Integer>();
         for (AVMDifference diff : diffList)
         {
             if (!diff.isValid())
             {
                 throw new AVMSyncException("Malformed AVMDifference.");
             }
-            int colonOff = diff.getSourcePath().indexOf(':');
-            if (colonOff == -1)
+            // Snapshot the source if needed.
+            int version = diff.getSourceVersion();
+            if (version < 0)
             {
-                throw new AVMBadArgumentException("Invalid path.");
+                int colonOff = diff.getSourcePath().indexOf(':');
+                if (colonOff == -1)
+                {
+                    throw new AVMBadArgumentException("Invalid path.");
+                }
+                String storeName = diff.getSourcePath().substring(0, colonOff);
+                if (storeVersions.containsKey(storeName))
+                {
+                    // We've already snapshotted this store.
+                    version = storeVersions.get(storeName);
+                }
+                else
+                {
+                    version = fAVMService.createSnapshot(storeName);
+                }
             }
-            String storeName = diff.getSourcePath().substring(0, colonOff);
-            int version = fAVMService.createSnapshot(storeName);
             AVMNodeDescriptor srcDesc = fAVMService.lookup(version,
                                                            diff.getSourcePath(), true);
             if (srcDesc == null)