diff --git a/lib/casserver/cas.rb b/lib/casserver/cas.rb
index d652d217..7c269683 100644
--- a/lib/casserver/cas.rb
+++ b/lib/casserver/cas.rb
@@ -170,7 +170,7 @@ def validate_service_ticket(service, ticket, allow_proxy_tickets = false)
     if service.nil? or ticket.nil?
       error = Error.new(:INVALID_REQUEST, "Ticket or service parameter was missing in the request.")
       $LOG.warn "#{error.code} - #{error.message}"
-    elsif st = ServiceTicket.find_by_ticket(ticket)
+    elsif st = SPTicket.find_by_ticket(ticket)
       if st.consumed?
         error = Error.new(:INVALID_TICKET, "Ticket '#{ticket}' has already been used up.")
         $LOG.warn "#{error.code} - #{error.message}"
diff --git a/lib/casserver/model.rb b/lib/casserver/model.rb
index 28fcfb11..d7a22b22 100644
--- a/lib/casserver/model.rb
+++ b/lib/casserver/model.rb
@@ -18,6 +18,10 @@ class LoginTicket < ActiveRecord::Base
   class SPTicket < ActiveRecord::Base
     include Consumable
     include Ticket
+    
+    belongs_to :granted_by_tgt,
+      :class_name => 'CASServer::Model::TicketGrantingTicket',
+      :foreign_key => :granted_by_tgt_id
 
     if ActiveRecord::VERSION::STRING >= '3.2'
       self.table_name = 'casserver_st'
@@ -32,9 +36,6 @@ def matches_service?(service)
   end
 
   class ServiceTicket < SPTicket
-    belongs_to :granted_by_tgt,
-      :class_name => 'CASServer::Model::TicketGrantingTicket',
-      :foreign_key => :granted_by_tgt_id
     has_one :proxy_granting_ticket,
       :foreign_key => :created_by_st_id
   end
diff --git a/lib/casserver/server.rb b/lib/casserver/server.rb
index 77f7633a..2c1e5c55 100644
--- a/lib/casserver/server.rb
+++ b/lib/casserver/server.rb
@@ -529,18 +529,17 @@ def self.init_database!
             send_logout_notification_for_service_ticket(st) if config[:enable_single_sign_out]
             # TODO: Maybe we should do some special handling if send_logout_notification_for_service_ticket fails?
             #       (the above method returns false if the POST results in a non-200 HTTP response).
+            pgts = CASServer::Model::ProxyGrantingTicket.find_all_by_service_ticket_id(st.id)
+
+            pgts.each do |pgt|
+              $LOG.debug("Deleting Proxy-Granting Ticket '#{pgt}' for user '#{pgt.service_ticket.username}'")
+              pgt.destroy
+            end
+
             $LOG.debug "Deleting #{st.class.name.demodulize} #{st.ticket.inspect} for service #{st.service}."
             st.destroy
           end
 
-          pgts = CASServer::Model::ProxyGrantingTicket.find(:all,
-            :conditions => [CASServer::Model::ServiceTicket.quoted_table_name+".username = ?", tgt.username],
-            :include => :service_ticket)
-          pgts.each do |pgt|
-            $LOG.debug("Deleting Proxy-Granting Ticket '#{pgt}' for user '#{pgt.service_ticket.username}'")
-            pgt.destroy
-          end
-
           $LOG.debug("Deleting #{tgt.class.name.demodulize} '#{tgt}' for user '#{tgt.username}'")
           tgt.destroy
         end