diff --git a/services/track-changes/app/coffee/PackManager.coffee b/services/track-changes/app/coffee/PackManager.coffee
index 4eba1bff2d..f6e4aa626c 100644
--- a/services/track-changes/app/coffee/PackManager.coffee
+++ b/services/track-changes/app/coffee/PackManager.coffee
@@ -281,7 +281,7 @@ module.exports = PackManager =
 				return callback(err) if err?
 				return callback() if not historyPacks?
 				# select only the new packs not already in the index
-				newPacks = (pack for pack in historyPacks when not indexResult[pack._id]?)
+				newPacks = (pack for pack in historyPacks when not indexResult?[pack._id]?)
 				newPacks = (_.omit(pack, 'doc_id', 'project_id', 'n', 'sz') for pack in newPacks)
 				logger.log {project_id, doc_id, n: newPacks.length}, "found new packs"
 				callback(null, newPacks)