diff --git a/kernel/debug.c b/kernel/debug.c
index c946bc9ec..d32d17517 100644
--- a/kernel/debug.c
+++ b/kernel/debug.c
@@ -9,6 +9,7 @@
 
 #include <minix/callnr.h>
 #include <minix/sysutil.h>
+#include <minix/u64.h>
 #include <limits.h>
 #include <string.h>