diff --git a/src/rules.vue b/src/rules.vue
index 92b07f4..aae7180 100644
--- a/src/rules.vue
+++ b/src/rules.vue
@@ -1058,7 +1058,7 @@ export default {
             return false
           }
 
-          if (field.type === 'duration' && !this.validateDuration(action.attributes[field.key], field.optional)) {
+          if (field.type === 'duration' && !this.validateDuration(action.attributes[field.key], !field.optional)) {
             this.validateReason = `${action.type} -> ${field.key} -> duration`
             return false
           }