diff --git a/src/structs.h b/src/structs.h
index bcf9d03..78108c1 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1494,6 +1494,10 @@
     int		class_refcount;
     int		class_copyID;		// used by garbage collection
 
+    // interfaces declared for the class
+    int		class_interface_count;
+    char_u	**class_interfaces;	// allocated array of names
+
     // class members: "static varname"
     int		class_class_member_count;
     ocmember_T	*class_class_members;	// allocated