diff --git a/ChangeLog b/ChangeLog
index df6518426..4e8222a18 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -10,6 +10,8 @@
 
 	* OpenChange/MAPIStoreGCSFolder.m
 	(-predecessorChangeListForMessageWithKey:): same as below.
+	(-setChangeKey:forMessageWithKey:): synchronise the version cache
+	if the message entry is not found.
 
 	* OpenChange/MAPIStoreMailFolder.m
 	(-predecessorChangeListForMessageWithKey:): the returned list must
diff --git a/OpenChange/MAPIStoreGCSFolder.m b/OpenChange/MAPIStoreGCSFolder.m
index 0464b5b97..e5f6bbd65 100644
--- a/OpenChange/MAPIStoreGCSFolder.m
+++ b/OpenChange/MAPIStoreGCSFolder.m
@@ -500,7 +500,12 @@ static Class NSNumberK;
   messages = [[versionsMessage properties] objectForKey: @"Messages"];
   messageEntry = [messages objectForKey: messageKey];
   if (!messageEntry)
-    abort ();
+    {
+      [self synchroniseCache];
+      messageEntry = [messages objectForKey: messageKey];
+      if (!messageEntry)
+        abort ();
+    }
   [self _setChangeKey: changeKey forMessageEntry: messageEntry];
   
   [versionsMessage save];