diff --git a/sys/sys/kassert.h b/sys/sys/kassert.h
--- a/sys/sys/kassert.h
+++ b/sys/sys/kassert.h
@@ -38,6 +38,16 @@
 extern bool panicked;
 #define	KERNEL_PANICKED()	__predict_false(panicked)
 
+/*
+ * Try to trap accesses.
+ * TODO: use kmsan if available
+ */
+#ifdef	INVARIANTS
+#define DEBUG_POISON_POINTER(x) ({ x = (void *)(UINTPTR_MAX - 4096); })
+#else
+#define DEBUG_POISON_POINTER(x)
+#endif
+
 #ifdef	INVARIANTS		/* The option is always available */
 #define	VNASSERT(exp, vp, msg) do {					\
 	if (__predict_false(!(exp))) {					\