diff --git a/Libraries/LibGC/Forward.h b/Libraries/LibGC/Forward.h
index 98cf257c9cf..56c28e3589c 100644
--- a/Libraries/LibGC/Forward.h
+++ b/Libraries/LibGC/Forward.h
@@ -6,6 +6,8 @@
 
 #pragma once
 
+#include <AK/Types.h>
+
 namespace GC {
 
 class Cell;