diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index f338d23b112b5afd568e9cb2da6249197993c98d..dc6bf35e78840c4872e7005c6115a861661886aa 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2604,7 +2604,7 @@ static int kdb_per_cpu(int argc, const char **argv)
 		diag = kdbgetularg(argv[3], &whichcpu);
 		if (diag)
 			return diag;
-		if (!cpu_online(whichcpu)) {
+		if (whichcpu >= nr_cpu_ids || !cpu_online(whichcpu)) {
 			kdb_printf("cpu %ld is not online\n", whichcpu);
 			return KDB_BADCPUNUM;
 		}