diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index aef1727250..14f8437983 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -237,7 +237,7 @@ static void fw_cfg_bootsplash(FWCfgState *s)
 static void fw_cfg_reboot(FWCfgState *s)
 {
     const char *reboot_timeout = NULL;
-    int64_t rt_val = -1;
+    uint64_t rt_val = -1;
     uint32_t rt_le32;
 
     /* get user configuration */
@@ -247,10 +247,11 @@ static void fw_cfg_reboot(FWCfgState *s)
 
     if (reboot_timeout) {
         rt_val = qemu_opt_get_number(opts, "reboot-timeout", -1);
+
         /* validate the input */
-        if (rt_val < 0 || rt_val > 0xffff) {
+        if (rt_val > 0xffff && rt_val != (uint64_t)-1) {
             error_report("reboot timeout is invalid,"
-                         "it should be a value between 0 and 65535");
+                         "it should be a value between -1 and 65535");
             exit(1);
         }
     }