diff --git a/converter/other/pnmtotiffcmyk.c b/converter/other/pnmtotiffcmyk.c
index b7e3228..7b5a903 100644
--- a/converter/other/pnmtotiffcmyk.c
+++ b/converter/other/pnmtotiffcmyk.c
@@ -967,8 +967,8 @@ int main( int argc, char **argv ) {
 
   if ( (err = parseOpts( argc, argv, rt )) ) goto exit ;
   
-  if ( (err = rt->in->open( rt->in, rt )) ) goto exit ;
-  if ( (err = rt->out->open( rt->out, rt )) ) goto exit ;
+  if ( (err = (rt->in->open)( rt->in, rt )) ) goto exit ;
+  if ( (err = (rt->out->open)( rt->out, rt )) ) goto exit ;
 
   while ( rt->in->hasMore( rt->in ) ) {
     if ( (err = rt->in->next( rt->in, &r, &g, &b )) ) goto exit ;