diff --git a/sys/arm64/arm64/machdep.c b/sys/arm64/arm64/machdep.c
--- a/sys/arm64/arm64/machdep.c
+++ b/sys/arm64/arm64/machdep.c
@@ -855,6 +855,10 @@
 
 	dbg_init();
 	kdb_init();
+#ifdef KDB
+	if ((boothowto & RB_KDB) != 0)
+		kdb_enter(KDB_WHY_BOOTFLAGS, "Boot flags requested debugger");
+#endif
 	pan_enable();
 
 	kcsan_cpu_init(0);
diff --git a/sys/riscv/riscv/machdep.c b/sys/riscv/riscv/machdep.c
--- a/sys/riscv/riscv/machdep.c
+++ b/sys/riscv/riscv/machdep.c
@@ -587,6 +587,10 @@
 	mutex_init();
 	init_param2(physmem);
 	kdb_init();
+#ifdef KDB
+	if ((boothowto & RB_KDB) != 0)
+		kdb_enter(KDB_WHY_BOOTFLAGS, "Boot flags requested debugger");
+#endif
 
 	env = kern_getenv("kernelname");
 	if (env != NULL)