diff --git a/app/models/rate.rb b/app/models/rate.rb
index 9db4aab..e1fe998 100644
--- a/app/models/rate.rb
+++ b/app/models/rate.rb
@@ -26,7 +26,10 @@ class Rate < ActiveRecord::Base
   
   # API to find the Rate for a +user+ on a +project+ at a +date+
   def self.for(user, project = nil, date = Date.today.to_s)
+    # Check input since it's a "public" API
     return nil unless user.is_a?(User)
+    return nil unless project.nil? || project.is_a?(Project)
+    
     rate = self.for_user_project_and_date(user, project, date)
     
     return nil if rate.nil?
diff --git a/spec/models/rate_spec.rb b/spec/models/rate_spec.rb
index 314a6a2..5868e57 100644
--- a/spec/models/rate_spec.rb
+++ b/spec/models/rate_spec.rb
@@ -196,6 +196,13 @@ describe Rate, 'for' do
     Rate.should_not_receive(:for_user_project_and_date)
     Rate.for(object).should be_nil
   end
+  
+  it 'with an invalid project should be nil' do
+    object = mock('random_object_with_id_attribute')
+    Rate.should_not_receive(:for_user_project_and_date)
+    Rate.for(@user, object).should be_nil
+  end
+  
 end
 
 describe Rate, 'for_user_project_and_date (private)' do