--- a/vehicle.c	Sat Feb 24 01:39:59 2007 +0000
+++ b/vehicle.c	Sat Feb 24 01:47:26 2007 +0000
@@ -514,6 +514,7 @@
 	Vehicle* u;
 
 	assert(v != NULL);
+	assert(v->type == VEH_Train);
 
 	if (v->first != NULL) {
 		if (IsFrontEngine(v->first) || IsFreeWagon(v->first)) return v->first;