--- a/src/vehicle.cpp	Mon Aug 06 06:23:44 2007 +0000
+++ b/src/vehicle.cpp	Mon Aug 06 11:58:15 2007 +0000
@@ -2554,6 +2554,7 @@
 {
 	assert(IsPlayerBuildableVehicleType(type));
 
+	if (!IsValidPlayer(_current_player)) return false;
 	if (_patches.always_build_infrastructure) return true;
 
 	UnitID max;