diff --git a/usr.bin/kdump/kdump.c b/usr.bin/kdump/kdump.c
--- a/usr.bin/kdump/kdump.c
+++ b/usr.bin/kdump/kdump.c
@@ -955,7 +955,9 @@
 				narg -= 2;
 				break;
 			case SYS_wait4:
-				print_number(ip, narg, c);
+				if ((pid_t)*ip == (pid_t)-1)
+					*ip = -1;
+				print_decimal_number(ip, narg, c);
 				print_number(ip, narg, c);
 				putchar(',');
 				print_mask_arg0(sysdecode_wait4_options, *ip);
@@ -968,7 +970,7 @@
 				c = ',';
 				ip++;
 				narg--;
-				print_number64(first, ip, narg, c);
+				print_decimal_number64(first, ip, narg, c);
 				print_number(ip, narg, c);
 				putchar(',');
 				print_mask_arg(sysdecode_wait6_options, *ip);