--- loncom/interface/loncommon.pm	2005/11/22 00:01:41	1.298
+++ loncom/interface/loncommon.pm	2005/11/22 22:33:01	1.299
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # a pile of common routines
 #
-# $Id: loncommon.pm,v 1.298 2005/11/22 00:01:41 raeburn Exp $
+# $Id: loncommon.pm,v 1.299 2005/11/22 22:33:01 foxr Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -3486,7 +3486,10 @@ sub no_cache {
 
 sub content_type {
     my ($r,$type,$charset) = @_;
-    &no_cache($r);
+    if ($r) {
+	#  Note that printout.pl calls this with undef for $r.
+	&no_cache($r);
+    }
     if ($env{'browser.mathml'} && $type eq 'text/html') { $type='text/xml'; }
     unless ($charset) {
 	$charset=&Apache::lonlocal::current_encoding;