diff --git a/src/www/system_gateways_edit.php b/src/www/system_gateways_edit.php
index 369bafadd..c25977dbd 100644
--- a/src/www/system_gateways_edit.php
+++ b/src/www/system_gateways_edit.php
@@ -287,6 +287,8 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
             $input_errors[] = gettext("The time period needs to be a numeric value.");
         } elseif ($pconfig['time_period'] < 1) {
             $input_errors[] = gettext("The time period needs to be positive.");
+        } elseif ($pconfig['time_period'] < (2.1*$pconfig['interval'])) {
+            $input_errors[] = gettext("The time period needs at least 2.1 times that of the probe interval.");
         }
     }