diff --git a/app/Http/Requests/Setting/Module.php b/app/Http/Requests/Setting/Module.php
index 940f8046e..ea2908005 100644
--- a/app/Http/Requests/Setting/Module.php
+++ b/app/Http/Requests/Setting/Module.php
@@ -27,12 +27,16 @@ class Module extends FormRequest
 
         $module = module($this->request->get('module_alias'));
 
-        if ($module->get('settings')) {
-            foreach ($module->get('settings') as $field) {
-                if (isset($field['rules'])) {
-                    $rules[$field['name']] = $field['rules'];
-                }
+        if (!$fields = $module->get('settings')) {
+            return $rules;
+        }
+
+        foreach ($fields as $field) {
+            if (empty($field['rules'])) {
+                continue;
             }
+
+            $rules[$field['name']] = $field['rules'];
         }
 
         return $rules;
diff --git a/modules/PaypalStandard/module.json b/modules/PaypalStandard/module.json
index c633dbd9f..fc7ed3410 100644
--- a/modules/PaypalStandard/module.json
+++ b/modules/PaypalStandard/module.json
@@ -21,7 +21,7 @@
             "attributes": {
                 "required": "required"
             },
-            "rules": "required"
+            "rules": "required|string"
         },
         {
             "type": "textGroup",
@@ -31,7 +31,7 @@
             "attributes": {
                 "required": "required"
             },
-            "rules": "required"
+            "rules": "required|email"
         },
         {
             "type": "selectGroup",
@@ -42,8 +42,11 @@
                 "live": "Live",
                 "sandbox": "Sandbox"
             },
-            "selected": null,
-            "attributes": {}
+            "selected": "live",
+            "attributes": {
+                "required": "required"
+            },
+            "rules": "required|string"
         },
         {
             "type": "selectGroup",
@@ -54,8 +57,11 @@
                 "authorization": "Authorization",
                 "sale": "Sale"
             },
-            "selected": null,
-            "attributes": {}
+            "selected": "sale",
+            "attributes": {
+                "required": "required"
+            },
+            "rules": "required|string"
         },
         {
             "type": "radioGroup",
@@ -63,7 +69,8 @@
             "title": "paypal-standard::general.form.customer",
             "enable": "general.yes",
             "disable": "general.no",
-            "attributes": {}
+            "attributes": {},
+            "rules": "required|integer"
         },
         {
             "type": "radioGroup",
@@ -71,14 +78,16 @@
             "title": "paypal-standard::general.form.debug",
             "enable": "general.yes",
             "disable": "general.no",
-            "attributes": {}
+            "attributes": {},
+            "rules": "required|integer"
         },
         {
             "type": "textGroup",
             "name": "order",
             "title": "paypal-standard::general.form.order",
             "icon": "sort",
-            "attributes": {}
+            "attributes": {},
+            "rules": "nullable|integer"
         }
     ]
 }