diff --git a/UI/MailPartViewers/UIxMailPartICalViewer.m b/UI/MailPartViewers/UIxMailPartICalViewer.m
index ec8c18af8..39585d08f 100644
--- a/UI/MailPartViewers/UIxMailPartICalViewer.m
+++ b/UI/MailPartViewers/UIxMailPartICalViewer.m
@@ -25,6 +25,8 @@
   Show plain/calendar mail parts.
 */
 
+#import <NGObjWeb/WOResponse.h>
+
 #import <NGExtensions/NSCalendarDate+misc.h>
 #import <NGExtensions/NSNull+misc.h>
 #import <NGExtensions/NSObject+Logs.h>