diff --git a/aircraft_cmd.c b/aircraft_cmd.c
index b66d0d6e7f..f853b088a7 100644
--- a/aircraft_cmd.c
+++ b/aircraft_cmd.c
@@ -360,13 +360,15 @@ int32 CmdSellAircraft(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
-	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
 
 	v = GetVehicle(p1);
 
 	if (v->type != VEH_Aircraft || !CheckOwnership(v->owner) || !CheckStoppedInHangar(v))
 		return CMD_ERROR;
 
+	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+
 	if (flags & DC_EXEC) {
 		// Invalidate depot
 		InvalidateWindow(WC_VEHICLE_DEPOT, v->tile);
@@ -385,9 +387,11 @@ int32 CmdStartStopAircraft(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Aircraft || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	// cannot stop airplane when in flight, or when taking off / landing
@@ -417,9 +421,11 @@ int32 CmdSendAircraftToHangar(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 	Station *st;
 	uint16 next_airport_index;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Aircraft || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (HASBIT(p2, 16)) v->set_for_replacement = true; //now all clients knows that the vehicle wants to be replaced
@@ -465,9 +471,11 @@ int32 CmdChangeAircraftServiceInt(int x, int y, uint32 flags, uint32 p1, uint32
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Aircraft || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
@@ -490,13 +498,19 @@ int32 CmdRefitAircraft(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 	byte new_cargo_type = p2 & 0xFF; //gets the cargo number
 	AircraftVehicleInfo *avi;
 
-	SET_EXPENSES_TYPE(EXPENSES_AIRCRAFT_RUN);
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
 
 	v = GetVehicle(p1);
+
+	if (v->type != VEH_Aircraft) return CMD_ERROR;
+
 	avi = AircraftVehInfo(v->engine_type);
+
 	if (!CheckOwnership(v->owner) || (!CheckStoppedInHangar(v) && !(SkipStoppedInHangerCheck)))
 		return CMD_ERROR;
 
+	SET_EXPENSES_TYPE(EXPENSES_AIRCRAFT_RUN);
+
 	switch (new_cargo_type) {
 		case CT_PASSENGERS:
 			pass = avi->passenger_capacity;
diff --git a/roadveh_cmd.c b/roadveh_cmd.c
index 1ad6d7104b..21b28c41a0 100644
--- a/roadveh_cmd.c
+++ b/roadveh_cmd.c
@@ -209,6 +209,8 @@ int32 CmdStartStopRoadVeh(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
 	if (v->type != VEH_Road || !CheckOwnership(v->owner))
@@ -229,13 +231,15 @@ int32 CmdSellRoadVeh(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
-	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
 
 	v = GetVehicle(p1);
 
 	if (v->type != VEH_Road || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
+	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+
 	if (!IsRoadDepotTile(v->tile) || v->u.road.state != 254 || !(v->vehstatus&VS_STOPPED))
 		return_cmd_error(STR_9013_MUST_BE_STOPPED_INSIDE);
 
@@ -307,9 +311,13 @@ static int FindClosestRoadDepot(Vehicle *v)
 		 bit 2 = clear v->set_for_replacement */
 int32 CmdSendRoadVehToDepot(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
-	Vehicle *v = GetVehicle(p1);
+	Vehicle *v;
 	int depot;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
+	v = GetVehicle(p1);
+
 	if (v->type != VEH_Road || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
@@ -348,6 +356,8 @@ int32 CmdTurnRoadVeh(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
 	if (v->type != VEH_Road || !CheckOwnership(v->owner))
@@ -373,6 +383,8 @@ int32 CmdChangeRoadVehServiceInt(int x, int y, uint32 flags, uint32 p1, uint32 p
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
 	if (v->type != VEH_Road || !CheckOwnership(v->owner))
diff --git a/ship_cmd.c b/ship_cmd.c
index 0bab059ba4..dec18586f8 100644
--- a/ship_cmd.c
+++ b/ship_cmd.c
@@ -915,13 +915,15 @@ int32 CmdSellShip(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
-	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
 
 	v = GetVehicle(p1);
 
 	if (v->type != VEH_Ship || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
+	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+
 	if (!IsShipDepotTile(v->tile) || v->u.road.state != 0x80 || !(v->vehstatus&VS_STOPPED))
 		return_cmd_error(STR_980B_SHIP_MUST_BE_STOPPED_IN);
 
@@ -943,9 +945,11 @@ int32 CmdStartStopShip(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Ship || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
@@ -969,9 +973,11 @@ int32 CmdSendShipToDepot(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 	Vehicle *v;
 	int depot;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Ship || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (HASBIT(p2, 0)) v->set_for_replacement = true;
@@ -1007,9 +1013,11 @@ int32 CmdChangeShipServiceInt(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Ship || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
@@ -1031,10 +1039,12 @@ int32 CmdRefitShip(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 	byte SkipStoppedInDepotCheck = (p2 & 0x100) >> 8; //excludes the cargo value
 
 	p2 = p2 & 0xFF;
-	SET_EXPENSES_TYPE(EXPENSES_SHIP_RUN);
+
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
 
 	v = GetVehicle(p1);
-	if (!CheckOwnership(v->owner))
+
+	if (v->type != VEH_Ship || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (!( SkipStoppedInDepotCheck )) {
@@ -1044,6 +1054,8 @@ int32 CmdRefitShip(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 			return_cmd_error(STR_980B_SHIP_MUST_BE_STOPPED_IN);
 		}
 
+	SET_EXPENSES_TYPE(EXPENSES_SHIP_RUN);
+
 	cost = 0;
 	if (IS_HUMAN_PLAYER(v->owner) && (byte)p2 != v->cargo_type) {
 		cost = _price.ship_base >> 7;
diff --git a/train_cmd.c b/train_cmd.c
index b0951b53ec..9c176c8df1 100644
--- a/train_cmd.c
+++ b/train_cmd.c
@@ -719,7 +719,10 @@ int32 CmdMoveRailVehicle(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 	Vehicle *src, *dst, *src_head, *dst_head;
 	bool is_loco;
 
+	if (!IsVehicleIndex(p1 & 0xFFFF)) return CMD_ERROR;
+
 	src = GetVehicle(p1 & 0xFFFF);
+
 	if (src->type != VEH_Train) return CMD_ERROR;
 
 	is_loco = !(RailVehInfo(src->engine_type)->flags & RVI_WAGON)
@@ -864,9 +867,11 @@ int32 CmdStartStopTrain(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Train || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
@@ -888,13 +893,15 @@ int32 CmdSellRailWagon(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 	Vehicle *v, *first,*last;
 	int32 cost;
 
-	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
 
 	v = GetVehicle(p1);
 
 	if (v->type != VEH_Train || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
+	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+
 	// get first vehicle in chain
 	first = v;
 	if (first->subtype != TS_Front_Engine) {
@@ -1172,9 +1179,11 @@ int32 CmdReverseTrainDirection(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Train || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	_error_message = STR_EMPTY;
@@ -1201,9 +1210,11 @@ int32 CmdForceTrainProceed(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
 	Vehicle *v;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
-	if (!CheckOwnership(v->owner))
+	if (v->type != VEH_Train || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (flags & DC_EXEC)
@@ -1225,12 +1236,15 @@ int32 CmdRefitRailVehicle(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 
 	p2 = p2 & 0xFF;
 
-	SET_EXPENSES_TYPE(EXPENSES_TRAIN_RUN);
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
 
 	v = GetVehicle(p1);
-	if (!CheckOwnership(v->owner) || ((CheckStoppedInDepot(v) < 0) && !(SkipStoppedInDepotCheck)))
+
+	if (v->type != VEH_Train || !CheckOwnership(v->owner) || ((CheckStoppedInDepot(v) < 0) && !(SkipStoppedInDepotCheck)))
 		return CMD_ERROR;
 
+	SET_EXPENSES_TYPE(EXPENSES_TRAIN_RUN);
+
 	cost = 0;
 	num = 0;
 
@@ -1341,10 +1355,14 @@ static TrainFindDepotData FindClosestTrainDepot(Vehicle *v)
 		 bit 2 = clear v->set_for_replacement */
 int32 CmdTrainGotoDepot(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
-	Vehicle *v = GetVehicle(p1);
+	Vehicle *v;
 	TrainFindDepotData tfdd;
 
-	if (!CheckOwnership(v->owner))
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
+	v = GetVehicle(p1);
+
+	if (v->type != VEH_Train || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (HASBIT(p2, 0)) v->set_for_replacement = true;
@@ -1387,9 +1405,13 @@ int32 CmdTrainGotoDepot(int x, int y, uint32 flags, uint32 p1, uint32 p2)
  */
 int32 CmdChangeTrainServiceInt(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 {
-	Vehicle *v = GetVehicle(p1);
+	Vehicle *v;
 
-	if (!CheckOwnership(v->owner))
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
+	v = GetVehicle(p1);
+
+	if (v->type != VEH_Train || !CheckOwnership(v->owner))
 		return CMD_ERROR;
 
 	if (flags & DC_EXEC) {
diff --git a/vehicle.c b/vehicle.c
index 9ebf7801b4..aa83185b5f 100644
--- a/vehicle.c
+++ b/vehicle.c
@@ -1331,13 +1331,15 @@ int32 CmdReplaceVehicle(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 	 the last 8 bit is the engine. The 8 bits in front of the engine is free so it have room for 16 bit engine entries */
 	uint16 new_engine_type = (uint16)(p2 & 0xFFFF);
 	uint32 autorefit_money = (p2  >> 16) * 100000;
-	Vehicle *v = GetVehicle(p1);
+	Vehicle *v, *u;
 	int cost, build_cost, rear_engine_cost = 0;
-	Vehicle *u = v;
-	byte old_engine_type = v->engine_type;
+	byte old_engine_type;
 
-	SET_EXPENSES_TYPE(EXPENSES_NEW_VEHICLES);
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
 
+	v = u = GetVehicle(p1);
+
+	old_engine_type = v->engine_type;
 
 	// first we make sure that it's a valid type the user requested
 	// check that it's an engine that is in the engine array
@@ -1636,6 +1638,8 @@ int32 CmdNameVehicle(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 	Vehicle *v;
 	StringID str;
 
+	if (!IsVehicleIndex(p1)) return CMD_ERROR;
+
 	v = GetVehicle(p1);
 
 	if (!CheckOwnership(v->owner))
diff --git a/vehicle.h b/vehicle.h
index 2a069e8b1f..8c626908a6 100644
--- a/vehicle.h
+++ b/vehicle.h
@@ -376,6 +376,14 @@ static inline Vehicle *GetVehicle(uint index)
 	return &_vehicles[index];
 }
 
+static inline bool IsVehicleIndex(uint index)
+{
+	if (index < _vehicles_size)
+		return true;
+	else
+		return false;
+}
+
 #define FOR_ALL_VEHICLES(v) for(v = _vehicles; v != &_vehicles[_vehicles_size]; v++)
 #define FOR_ALL_VEHICLES_FROM(v, from) for(v = GetVehicle(from); v != &_vehicles[_vehicles_size]; v++)