diff --git a/MeteorClient.py b/MeteorClient.py
index d16d69f..d44af2c 100644
--- a/MeteorClient.py
+++ b/MeteorClient.py
@@ -24,10 +24,12 @@ def add_data(self, collection, id, fields):
 
     def change_data(self, collection, id, fields, cleared):
         for key, value in fields.items():
-            self.data[collection][id][key] = value
+            if collection in self.data and id in self.data[collection]:
+                self.data[collection][id][key] = value
 
         for key in cleared:
-            del self.data[collection][id][key]
+            if collection in self.data and id in self.data[collection] and key in self.data[collection][id]:
+                del self.data[collection][id][key]
 
     def remove_data(self, collection, id):
         del self.data[collection][id]