diff --git a/mongo-query.coffee b/mongo-query.coffee
index e91de12..57b5ec2 100644
--- a/mongo-query.coffee
+++ b/mongo-query.coffee
@@ -83,6 +83,7 @@ projection = (query, proj) ->
 # optimize projection by removing overlaps
 optimizeProjection = (obj) ->
   keys = Object.keys(obj).sort()
+  return if keys.length <= 1
   for i in [1 ... keys.length]
     a = keys[i-1]
     b = keys[i]
diff --git a/presets.coffee b/presets.coffee
index af428b7..78e1c3e 100644
--- a/presets.coffee
+++ b/presets.coffee
@@ -66,7 +66,7 @@ matchObject = (object, param) ->
 exports.assertPresets = (deviceId, presetsHash, callback) ->
   getPresets((presets, objects) ->
     # only fetch relevant params
-    projection = {}
+    projection = {_id : 1}
     for p in presets
       p.precondition = query.expand(p.precondition)
       mongoQuery.projection(p.precondition, projection)