diff --git a/src/Umbraco.Core/Services/IdkMap.cs b/src/Umbraco.Core/Services/IdkMap.cs
index 7cf69f2e64..c1981b7b80 100644
--- a/src/Umbraco.Core/Services/IdkMap.cs
+++ b/src/Umbraco.Core/Services/IdkMap.cs
@@ -76,8 +76,9 @@ namespace Umbraco.Core.Services
                 _locker.EnterWriteLock();
                 foreach (var pair in pairs)
                 {
-                    _id2Key.Add(pair.id, new TypedId<Guid>(pair.key, umbracoObjectType));
-                    _key2Id.Add(pair.key, new TypedId<int>(pair.id, umbracoObjectType));
+
+                    _id2Key[pair.id] = new TypedId<Guid>(pair.key, umbracoObjectType);
+                    _key2Id[pair.key] = new TypedId<int>(pair.id, umbracoObjectType);
                 }
             }
             finally
diff --git a/src/Umbraco.Web/Trees/ContentTreeControllerBase.cs b/src/Umbraco.Web/Trees/ContentTreeControllerBase.cs
index e8ba964f98..4705e16c7e 100644
--- a/src/Umbraco.Web/Trees/ContentTreeControllerBase.cs
+++ b/src/Umbraco.Web/Trees/ContentTreeControllerBase.cs
@@ -96,6 +96,12 @@ namespace Umbraco.Web.Trees
                 return null;
 
             var treeNode = GetSingleTreeNode(e, parentId, queryStrings);
+            if (treeNode == null)
+            {
+                //this means that the user has NO access to this node via permissions! They at least need to have browse permissions to see
+                //the node so we need to return null;
+                return null;
+            }
             if (hasPathAccess == false)
             {
                 treeNode.AdditionalData["noAccess"] = true;