diff --git a/get-certs.sh b/get-certs.sh
index ddfd789..200176e 100755
--- a/get-certs.sh
+++ b/get-certs.sh
@@ -151,8 +151,14 @@ else
   exit 1
 fi
 
+# prepare to launche dnsmasq
 tmp_conf_file=$twd/dnsmasq.$USER.tmp.cnf
 
+# clean dnsmasq processes
+for p in `ps | grep dnsmasq.*.tmp.cnf | grep -v grep | awk '{print $1}'` ; do
+  kill $p ;
+done
+
 # launch acme challenge dnsmasq process
 touch $tmp_conf_file \
   && dnsmasq \
@@ -193,14 +199,12 @@ echo "Waiting for $wait_before_renew seconds."
 sleep $wait_before_renew
 
 # issue certificate
+export MAX_RETRY_TIMES=40
 $acme_cmd --renew --server $tls_provider \
   -d "$domain" \
   --dns $long_flag
 acme_renew_state=$?
 
-# kill acme challenge dnsmasq process
-kill $acme_dnsmasq_pid
-
 rm $tmp_conf_file
 
 echo ""