diff --git a/tool/run/load.inc b/tool/run/load.inc
index 4d540248ed..6f5e196696 100644
--- a/tool/run/load.inc
+++ b/tool/run/load.inc
@@ -3,5 +3,7 @@
 #
 proc load_spawn_id { } {
 	global load_spawn_id
-	return $load_spawn_id
+	if {[info exists load_spawn_id]} {
+		return $load_spawn_id }
+	return -1
 }