diff --git a/UI/PreferencesUI/UIxJSONPreferences.m b/UI/PreferencesUI/UIxJSONPreferences.m
index 6ef652a07..97ed67c0e 100644
--- a/UI/PreferencesUI/UIxJSONPreferences.m
+++ b/UI/PreferencesUI/UIxJSONPreferences.m
@@ -345,7 +345,7 @@ static SoProduct *preferencesProduct = nil;
 
   // Add the domain's default vacation subject if user has not specified a custom subject
   vacationOptions = [defaults vacationOptions];
-  if (![vacationOptions objectForKey: @"customSubject"] && [domainDefaults vacationDefaultSubject])
+  if (![[vacationOptions objectForKey: @"customSubject"] length] && [domainDefaults vacationDefaultSubject])
     {
       if (vacationOptions)
         vacation = [NSMutableDictionary dictionaryWithDictionary: vacationOptions];
diff --git a/UI/Templates/PreferencesUI/UIxPreferences.wox b/UI/Templates/PreferencesUI/UIxPreferences.wox
index 71d7949f0..c6a64996b 100644
--- a/UI/Templates/PreferencesUI/UIxPreferences.wox
+++ b/UI/Templates/PreferencesUI/UIxPreferences.wox
@@ -839,6 +839,7 @@
                   <md-input-container class="md-block md-flex">
                     <label><var:string label:value="Auto reply subject"/></label>
                     <input type="text"
+                           ng-required="app.preferences.defaults.Vacation.customSubjectEnabled"
                            ng-disabled="!app.preferences.defaults.Vacation.customSubjectEnabled"
                            ng-model="app.preferences.defaults.Vacation.customSubject"/>
                     <div class="sg-hint" ng-show="app.sieveVariablesCapability">