diff --git a/webmails/roundcube/config.inc.php b/webmails/roundcube/config.inc.php
index 635f7207..b02c527e 100644
--- a/webmails/roundcube/config.inc.php
+++ b/webmails/roundcube/config.inc.php
@@ -13,7 +13,7 @@ $config['log_driver'] = 'stdout';
 $config['zipdownload_selection'] = true;
 $config['enable_spellcheck'] = true;
 $config['spellcheck_engine'] = 'pspell';
-$config['session_lifetime'] = {{ SESSION_TIMEOUT }}; //60
+$config['session_lifetime'] = {{ SESSION_TIMEOUT_MINUTES | int }};
 
 // Mail servers
 $config['default_host'] = '{{ FRONT_ADDRESS or "front" }}';
diff --git a/webmails/roundcube/start.py b/webmails/roundcube/start.py
index 13cbdd42..db9e5ccd 100755
--- a/webmails/roundcube/start.py
+++ b/webmails/roundcube/start.py
@@ -62,6 +62,10 @@ context["PLUGINS"] = ",".join(f"'{p}'" for p in plugins)
 # add overrides
 context["INCLUDES"] = sorted(inc for inc in os.listdir("/overrides") if inc.endswith(".inc")) if os.path.isdir("/overrides") else []
 
+# calculate variables for config file
+env["SESSION_TIMEOUT_MINUTES"] = str(int(env.get("SESSION_TIMEOUT", "3600")) // 60 ) if int(env.get("SESSION_TIMEOUT", "3600")) >= 60 else "1"
+context.update(env)
+
 # create config files
 conf.jinja("/php.ini", context, "/usr/local/etc/php/conf.d/roundcube.ini")
 conf.jinja("/config.inc.php", context, "/var/www/html/config/config.inc.php")