Index: man.sh
===================================================================
diff --git a/head/usr.bin/man/man.sh b/head/usr.bin/man/man.sh
--- a/head/usr.bin/man/man.sh	(revision 274850)
+++ b/head/usr.bin/man/man.sh	(working copy)
@@ -276,11 +276,8 @@
 	return 0
 }
 
-# Usage: man_display_page
-# Display either the manpage or catpage depending on the use_cat variable
 man_display_page() {
-	local EQN NROFF PIC TBL TROFF REFER VGRIND
-	local IFS l nroff_dev pipeline preproc_arg tool
+	local IFS pipeline preconv_enc testline
 
 	# We are called with IFS set to colon. This causes really weird
 	# things to happen for the variables that have spaces in them.
@@ -312,6 +309,42 @@
 		return
 	fi
 
+	case "${manpage}" in
+	*.${man_charset}/*)
+		case "$man_charset" in
+		ISO8859-1) preconv_enc="latin-1" ;;
+		ISO8859-15) preconv_enc="latin-1" ;;
+		UTF-8) preconv_enc="utf-8" ;;
+		esac
+		;;
+	esac
+
+	if [ -n "$preconv_enc" ]; then
+		pipeline="preconv -e $preconv_enc |"
+	fi
+	testline="$pipeline mandoc -Tlint -Werror 2>/dev/null"
+	pipeline="$pipeline mandoc -Tlocale | $MANPAGER"
+
+	if ! eval "$cattool $manpage | $testline" ;then
+		man_display_page_groff
+		return
+	fi
+
+	if [ $debug -gt 0 ]; then
+		decho "Command: $cattool $manpage | $pipeline"
+		ret=0
+	else
+		eval "$cattool $manpage | $pipeline"
+		ret=$?
+	fi
+}
+
+# Usage: man_display_page
+# Display either the manpage or catpage depending on the use_cat variable
+man_display_page_groff() {
+	local EQN NROFF PIC TBL TROFF REFER VGRIND
+	local IFS l nroff_dev pipeline preproc_arg tool
+
 	# So, we really do need to parse the manpage. First, figure out the
 	# device flag (-T) we have to pass to eqn(1) and groff(1). Then,
 	# setup the pipeline of commands based on the user's request.