diff --git a/lib/storage_room/identity_map.rb b/lib/storage_room/identity_map.rb
index <HASH>..<HASH> 100644
--- a/lib/storage_room/identity_map.rb
+++ b/lib/storage_room/identity_map.rb
@@ -8,7 +8,7 @@ module StorageRoom
     end
     
     def self.models
-      @models ||= Set.new
+      @models ||= ::Set.new
     end
 
     def self.clear
diff --git a/spec/storage_room/identity_map_spec.rb b/spec/storage_room/identity_map_spec.rb
index <HASH>..<HASH> 100644
--- a/spec/storage_room/identity_map_spec.rb
+++ b/spec/storage_room/identity_map_spec.rb
@@ -15,7 +15,7 @@ describe StorageRoom::IdentityMap do
     describe "#models" do
       it "should return set" do
         set = StorageRoom::IdentityMap.models
-        set.should be_an_instance_of(Set)
+        set.should be_an_instance_of(::Set)
         set.should include(StorageRoom::Resource)
       end
     end
Fix a problem with the identity map