diff --git a/lib/openmsx/share/scripts/fail_after.tcl b/lib/openmsx/share/scripts/fail_after.tcl
index 8e590d9..7a8ed57 100644
--- a/lib/openmsx/share/scripts/fail_after.tcl
+++ b/lib/openmsx/share/scripts/fail_after.tcl
@@ -2,7 +2,7 @@
 #
 # Typically used in combination with the MSX-DOS 'omsxctl.com' utility.
 #
-# Adds two environment variables and two commands to openMSX;
+# Adds two commands to openMSX;
 #
 # 'fail_after timeout [timeunit] [fail_id] [fail_code]'
 # Schedules an openMSX exit after the timeout.
@@ -54,17 +54,26 @@ proc fail_after { timeout {time_unit "time"} {fail_id "fail_after"} {fail_code 2
 			puts stderr "error: $err_msg"
 			fail_after_exit fail_after_timer_error 1
 		}
-		set msg "$msg\n$fail_id: Automatic failure in $timeout $time_unit seconds."
+		set msg "$msg\n$fail_id: Failure in $timeout $time_unit sec"
 	} else {
 		set fail_after_prev_timer 0
 	}
 	return $msg
 }
 
+proc fail_after_reboot_watchdog {} {
+	global fail_after_boot_timeout
+	if {$fail_after_boot_timeout != 0} {
+		fail_after $fail_after_boot_timeout realtime failed_boot 124
+		after boot "fail_after_reboot_watchdog"
+	}
+}
+
 # Globals
 set fail_after_prev_timer 0
 set fail_after_prev_id 0
 set fail_after_path 0
+set fail_after_boot_timeout 0
 
 # Parse screenshot path env setting
 if {[info exists ::env(FAIL_AFTER_PATH)] && ([string trim $::env(FAIL_AFTER_PATH)] != "")} {
@@ -73,5 +82,6 @@ if {[info exists ::env(FAIL_AFTER_PATH)] && ([string trim $::env(FAIL_AFTER_PATH
 
 # Enables boot watch dog timer when FAIL_AFTER_BOOT env has a value. (124 see `man timeout`) 
 if {[info exists ::env(FAIL_AFTER_BOOT)] && ([string trim $::env(FAIL_AFTER_BOOT)] != "")} {
-	fail_after [string trim $::env(FAIL_AFTER_BOOT)] realtime failed_boot 124
+	set fail_after_boot_timeout [string trim $::env(FAIL_AFTER_BOOT)]
+	fail_after_reboot_watchdog
 }