diff --git a/s4-funcs.sh b/s4-funcs.sh
index d812053..faa492a 100755
--- a/s4-funcs.sh
+++ b/s4-funcs.sh
@@ -56,6 +56,8 @@
 blogreadflagrowid=0
 blogcutoffflagrowid=-1
 whatsnewdays=${WHATS_NEW_DAYS:-14}
+main_session=`date +%F-$$`
+session=$main_session
 
 tconfs=""
 imgcached=cache/img.`date +%Y/%m`
@@ -677,10 +679,12 @@
 )
 setpar() {
   # 2020/5/14 Add dirty code to cache essential params
-  case "$1" in
-    user)	_user="$v" ;;
-    skey)	_skey="$v" ;;
-  esac
+  if [ x"$session" = x"$main_session" ]; then
+    case "$1" in
+      user)	_user="$v" ;;
+      skey)	_skey="$v" ;;
+    esac
+  fi
   query "replace into par values('$session', '$1', '$2', \"$3\");"
 }
 replpar() {
@@ -689,7 +693,7 @@
 getpar() {
   # err GETPAR=$1, _user=$_user
   val=""
-  if false; then	# 2020/6/3 Temporary disabled for joingrp()
+  if [ x"$session" = x"$main_session" ]; then
     case "$1" in	# Dirty cache mechanism for high-load average
       user)	val=$_user ;;
       skey)	val=$_skey ;;
@@ -1415,7 +1419,6 @@
 
 
 cgiinit() {
-  session=`date +%F-$$`
   tmpd=`tmpd=$tmpdir mktempd`
   tmpf=$tmpd/stream.$$
   tmpfiles=$tmpfiles" $tmpd"
@@ -3263,7 +3266,7 @@
   if [ -z "$2" ]; then
     echo "bye bye" | html p; return
   fi
-  t_usr=`session=$2 getpar user`
+  t_usr=`session=$2 getpar adduser`
   t_grp=`session=$2 getpar group`
   ## err joingrpadmit: t_usr=$t_usr, t_grp=$t_grp
   _m4 -D_TITLE_="joingrp" $layout/html.m4.html
@@ -3301,7 +3304,7 @@
   jss="joingrp-`date +%s`-`genrandom 12`"
   addsession $jss +${memoplimitdays}days
   query "replace into par values('$jss', 'group', 'string', `sqlquote \"$1\"`),
-('$jss', 'user', 'string', `sqlquote \"$user\"`);"
+('$jss', 'adduser', 'string', `sqlquote \"$user\"`);"
   smail "$(collectemail `getgroupadmins $1`)" "Join request to $1"<<EOF
 $url
 $user さんから