diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 14bc95abfe30d..15c3d7be364c7 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -1336,11 +1336,15 @@ def postgresql_version
           @connection.server_version
         end
 
+        # See http://www.postgresql.org/docs/9.1/static/errcodes-appendix.html
+        FOREIGN_KEY_VIOLATION = "23503"
+        UNIQUE_VIOLATION      = "23505"
+
         def translate_exception(exception, message)
-          case exception.message
-          when /duplicate key value violates unique constraint/
+          case exception.result.error_field(PGresult::PG_DIAG_SQLSTATE)
+          when UNIQUE_VIOLATION
             RecordNotUnique.new(message, exception)
-          when /violates foreign key constraint/
+          when FOREIGN_KEY_VIOLATION
             InvalidForeignKey.new(message, exception)
           else
             super