diff --git a/functions.inc.php b/functions.inc.php
index 3f88915f..b116951c 100644
--- a/functions.inc.php
+++ b/functions.inc.php
@@ -16,6 +16,7 @@
  */
 
 $version = '2.93';
+$min_db_version = 1835;  # update (at least) before a release with the latest function numbrer in upgrade.php
 
 /**
  * check_session
@@ -1754,7 +1755,34 @@ function table_by_key ($table_key) {
     return $CONF['database_prefix'].$table;
 }
 
+/*
+ * check if the database layout is up to date
+ * returns the current 'version' value from the config table
+ * if $error_out is True (default), die() with a message that recommends to run setup.php.
+ */
+function check_db_version($error_out = True) {
+    global $min_db_version;
 
+    $table = table_by_key('config');
+
+    $sql = "SELECT value FROM $table WHERE name = 'version'";
+    $r = db_query($sql);
+
+    if($r['rows'] == 1) {
+        $row = db_assoc($r['result']);
+        $dbversion = $row['value'];
+    } else {
+        $dbversion = 0;
+        db_query("INSERT INTO $table (name, value) VALUES ('version', '0')", 0, '');
+    }
+
+    if ( ($dbversion < $min_db_version) && $error_out == True) {
+        echo "ERROR: The PostfixAdmin database layout is outdated (you have r$dbversion, but r$min_db_version is expected).\nPlease run setup.php to upgrade the database.\n";
+        exit(1);
+    }
+
+    return $dbversion;
+}
 
 /*
    Called after an alias_domain has been deleted in the DBMS.
diff --git a/login.php b/login.php
index 4d83ae0d..42acda0c 100644
--- a/login.php
+++ b/login.php
@@ -34,6 +34,7 @@ if($CONF['configured'] !== true) {
     exit;
 }
 
+check_db_version(); # check if the database layout is up to date (and error out if not)
 
 if ($_SERVER['REQUEST_METHOD'] == "POST")
 {
diff --git a/scripts/postfixadmin-cli.php b/scripts/postfixadmin-cli.php
index b105e85d..904956bc 100644
--- a/scripts/postfixadmin-cli.php
+++ b/scripts/postfixadmin-cli.php
@@ -177,6 +177,9 @@ class PostfixAdmin {
             return false;
         }
 
+        # make sure global variables fron functions.inc.php end up in the global namespace, instead of being local to this function
+        global $version, $min_db_version;
+
         if (!require_once(PATH . '/common.php')) {
             $this->stderr("Failed to load " . PATH . '/common.php');
             return false;
@@ -190,6 +193,8 @@ class PostfixAdmin {
     public function dispatch() {
         $CONF = Config::read('all');
 
+        check_db_version(); # ensure the database layout is up to date
+
         if (!isset($this->args[0])) {
             $this->help();
             return;
diff --git a/upgrade.php b/upgrade.php
index ddaefa80..95e52eee 100644
--- a/upgrade.php
+++ b/upgrade.php
@@ -131,21 +131,7 @@ if($CONF['database_type'] == 'pgsql') {
     db_query_parsed($mysql, 0, " ENGINE = MYISAM COMMENT = 'PostfixAdmin settings'");
 }
 
-$sql = "SELECT * FROM $table WHERE name = 'version'";
-
-// insert into config('version', '01');
-
-$r = db_query($sql);
-
-if($r['rows'] == 1) {
-    $rs = $r['result'];
-    $row = db_array($rs);
-    $version = $row['value'];
-} else {
-    db_query_parsed("INSERT INTO $table (name, value) VALUES ('version', '0')", 0, '');
-    $version = 0;
-}
-
+$version = check_db_version(False);
 _do_upgrade($version);
 
 function _do_upgrade($current_version) {
diff --git a/users/login.php b/users/login.php
index e697c95f..41fbd214 100644
--- a/users/login.php
+++ b/users/login.php
@@ -30,6 +30,7 @@ $rel_path = '../';
 define('POSTFIXADMIN_LOGOUT', 1);
 require_once("../common.php");
 
+check_db_version(); # check if the database layout is up to date (and error out if not)
 
 if ($_SERVER['REQUEST_METHOD'] == "POST")
 {