diff --git a/src/order_cmd.cpp b/src/order_cmd.cpp
index 546065734b..516fd276a2 100644
--- a/src/order_cmd.cpp
+++ b/src/order_cmd.cpp
@@ -1005,6 +1005,7 @@ CommandCost CmdInsertOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 			if (occ >= OCC_END) return CMD_ERROR;
 			switch (new_order.GetConditionVariable()) {
 				case OCV_SLOT_OCCUPANCY: {
+					if (v->type != VEH_TRAIN) return CMD_ERROR;
 					TraceRestrictSlotID slot = new_order.GetXData();
 					if (slot != INVALID_TRACE_RESTRICT_SLOT_ID && !TraceRestrictSlot::IsValidID(slot)) return CMD_ERROR;
 					if (occ != OCC_IS_TRUE && occ != OCC_IS_FALSE) return CMD_ERROR;
@@ -1579,6 +1580,7 @@ CommandCost CmdModifyOrder(TileIndex tile, DoCommandFlag flags, uint32 p1, uint3
 
 		case MOF_COND_VARIABLE:
 			if (data == OCV_FREE_PLATFORMS && v->type != VEH_TRAIN) return CMD_ERROR;
+			if (data == OCV_SLOT_OCCUPANCY && v->type != VEH_TRAIN) return CMD_ERROR;
 			if (data >= OCV_END) return CMD_ERROR;
 			break;