diff --git a/tools/testing/selftests/powerpc/mm/tlbie_test.c b/tools/testing/selftests/powerpc/mm/tlbie_test.c
index 9868a5ddd84799410698f3bdb78f16a4d476eb4f..f85a0938ab25fefd2fa7e1214fd600a571b85456 100644
--- a/tools/testing/selftests/powerpc/mm/tlbie_test.c
+++ b/tools/testing/selftests/powerpc/mm/tlbie_test.c
@@ -636,7 +636,7 @@ int main(int argc, char *argv[])
 			nrthreads = strtoul(optarg, NULL, 10);
 			break;
 		case 'l':
-			strncpy(logdir, optarg, LOGDIR_NAME_SIZE);
+			strncpy(logdir, optarg, LOGDIR_NAME_SIZE - 1);
 			break;
 		case 't':
 			run_time = strtoul(optarg, NULL, 10);