diff --git a/lib/with_advisory_lock/postgresql.rb b/lib/with_advisory_lock/postgresql.rb
index 2e25ac6..330f786 100644
--- a/lib/with_advisory_lock/postgresql.rb
+++ b/lib/with_advisory_lock/postgresql.rb
@@ -8,12 +8,12 @@ def try_lock
       # pg_try_advisory_lock will either obtain the lock immediately
       # and return true, or return false if the lock cannot be acquired immediately
       sql = "SELECT pg_try_advisory_lock(#{numeric_lock}), #{Time.now.to_f}"
-      "t" == connection.select_value(sql).to_s
+      "t" == connection.execute(sql).first["pg_try_advisory_lock"].to_s
     end
 
     def release_lock
       sql = "SELECT pg_advisory_unlock(#{numeric_lock}), #{Time.now.to_f}"
-      "t" == connection.select_value(sql).to_s
+      "t" == connection.execute(sql).first["pg_advisory_unlock"].to_s
     end
 
     def numeric_lock(name=lock_name)