diff --git a/sortix/include/sortix/kernel/interrupt.h b/sortix/include/sortix/kernel/interrupt.h
index 8ac6a323..5247c5f1 100644
--- a/sortix/include/sortix/kernel/interrupt.h
+++ b/sortix/include/sortix/kernel/interrupt.h
@@ -25,6 +25,8 @@
 #ifndef INCLUDE_SORTIX_KERNEL_INTERRUPT_H
 #define INCLUDE_SORTIX_KERNEL_INTERRUPT_H
 
+#include <stddef.h>
+
 #include <sortix/kernel/decl.h>
 
 namespace Sortix {