diff --git a/lib/with_advisory_lock/postgresql.rb b/lib/with_advisory_lock/postgresql.rb
index 0740a62..4919e32 100644
--- a/lib/with_advisory_lock/postgresql.rb
+++ b/lib/with_advisory_lock/postgresql.rb
@@ -2,11 +2,17 @@ module WithAdvisoryLock
   class PostgreSQL < Base
     # See http://www.postgresql.org/docs/9.1/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
     def try_lock
-      execute_successful?('pg_try_advisory_lock')
+      if connection.open_transactions > 0
+        execute_successful?('pg_try_advisory_xact_lock')
+      else
+        execute_successful?('pg_try_advisory_lock')
+      end
     end
 
     def release_lock
-      execute_successful?('pg_advisory_unlock')
+      if connection.open_transactions <= 0
+        execute_successful?('pg_advisory_unlock')
+      end
     end
 
     def execute_successful?(pg_function)