diff --git a/dashboard/public/views/app.html b/dashboard/public/views/app.html
index c58698149..8bc182580 100644
--- a/dashboard/public/views/app.html
+++ b/dashboard/public/views/app.html
@@ -1159,10 +1159,10 @@
           <div class="col-md-12">
             <form role="form" name="devicesForm" ng-submit="resources.submitDevices()" autocomplete="off">
               <fieldset>
-                <div class="form-group" ng-class="{ 'has-error': resources.error.devices }">
+                <div class="form-group">
                   <label class="control-label" for="devicesInput">Devices <sup><a ng-href="https://docs.cloudron.io/apps/#devices" class="help" target="_blank"><i class="fa fa-question-circle"></i></a></sup></label>
                   <p>Comma serparated list of devices mounted into the app</p>
-                  <input type="text" class="form-control" id="devicesInput" ng-model="resources.devices" placeholder="/dev/ttyUSB, /dev/hidraw0, ..." ng-disabled="resources.busy"/>
+                  <input type="text" class="form-control" ng-class="{ 'has-error': resources.error.devices }" id="devicesInput" ng-model="resources.devices" placeholder="/dev/ttyUSB, /dev/hidraw0, ..." ng-disabled="resources.busy"/>
                   <span class="text-danger" ng-show="resources.error.devices">{{ resources.error.devices }}</span>
                 </div>
               </fieldset>
diff --git a/src/apps.js b/src/apps.js
index bdf499fda..2be6773da 100644
--- a/src/apps.js
+++ b/src/apps.js
@@ -486,7 +486,7 @@ function validateTags(tags) {
 
 function validateDevices(devices) {
     for (const key in devices) {
-        if (key.indexOf('/dev/' !== 0)) return new BoxError(BoxError.BAD_FIELD, 'devices must start with /dev/');
+        if (key.indexOf('/dev/') !== 0) return new BoxError(BoxError.BAD_FIELD, `"${key}" must start with /dev/`);
     }
 
     return null;