diff --git a/core/src/drop.h b/core/src/drop.h
index c5a9936..894b62d 100644
--- a/core/src/drop.h
+++ b/core/src/drop.h
@@ -1,6 +1,8 @@
 #ifndef _fencer_drop_h
 #define _fencer_drop_h
 
+#include "typeclass_helpers.h"
+
 typedef struct {
     void (*const drop)(void* self);
 } IDrop;