diff --git a/src/deb/vesta/postinst b/src/deb/vesta/postinst
index 3f237f10..e53fee72 100755
--- a/src/deb/vesta/postinst
+++ b/src/deb/vesta/postinst
@@ -26,8 +26,8 @@ fi
 # chmod a=rw /usr/local/vesta/data/upgrades/show_changelog
 
 # Fixing 'dh key too small' in dovecot
-if [ -f "/var/log/dovecot.log" ] && [ -f "/etc/dovecot/conf.d/10-ssl.conf" ] && [ -f "/usr/share/dovecot/dh.pem" ]; then
-    if grep -q 'dh key too small' /var/log/dovecot.log; then
+if [ -f "/var/log/dovecot.log.1" ] && [ -f "/etc/dovecot/conf.d/10-ssl.conf" ] && [ -f "/usr/share/dovecot/dh.pem" ]; then
+    if grep -q 'dh key too small' /var/log/dovecot.log.1; then
         if ! grep -q 'dh.pem' /etc/dovecot/conf.d/10-ssl.conf; then
             echo "== Fixing 'dh key too small' in dovecot"
             echo "ssl_dh=</usr/share/dovecot/dh.pem" >> /etc/dovecot/conf.d/10-ssl.conf