\begingroup

\catcode"C3=\active
\catcode"C5=\active
%
\def^^c3#1{%
	\ifx#1^^a6^^1a\else % æ - U+00E6 - ae
	\errmessage{Hyphenation pattern file corrupted or OT1 encoding not supported!}
\fi}
\def^^c5#1{%
	\ifx#1^^93^^1b\else % œ - U+0153 - oe
	\errmessage{Hyphenation pattern file corrupted or OT1 encoding not supported!}
\fi}
%
% ensure all the chars above have valid lccode values
%
\lccode"1A="1A % æ - U+00E6 - ae
\lccode"1B="1B % œ - U+0153 - oe

% Ligatures ae and oe (in OT1)
\patterns{
æ1
œ1
}
\endgroup
