diff --git a/OpenChange/SOGoGCSFolder+MAPIStore.h b/OpenChange/SOGoGCSFolder+MAPIStore.h
index 70b62d896..868e555ae 100644
--- a/OpenChange/SOGoGCSFolder+MAPIStore.h
+++ b/OpenChange/SOGoGCSFolder+MAPIStore.h
@@ -25,6 +25,8 @@
 
 #import <SOGo/SOGoGCSFolder.h>
 
+@class NSString;
+
 @interface SOGoGCSFolder (MAPIStore)
 
 - (NSArray *) componentKeysWithType: (NSString *) component;