diff --git a/src/core/execution/TradeShipExecution.ts b/src/core/execution/TradeShipExecution.ts
index 99663faad..fd7062ca5 100644
--- a/src/core/execution/TradeShipExecution.ts
+++ b/src/core/execution/TradeShipExecution.ts
@@ -16,9 +16,9 @@ import { distSortUnit } from "../Util";
 
 export class TradeShipExecution implements Execution {
   private active = true;
-  private mg: Game;
-  private origOwner: Player;
-  private tradeShip: Unit;
+  private mg: Game | null = null;
+  private origOwner: Player | null = null;
+  private tradeShip: Unit | null = null;
   private index = 0;
   private wasCaptured = false;
 
@@ -35,12 +35,15 @@ export class TradeShipExecution implements Execution {
   }
 
   tick(ticks: number): void {
-    if (this.tradeShip == null) {
+    if (this.mg === null || this.origOwner === null) {
+      throw new Error("Not initialized");
+    }
+    if (this.tradeShip === null) {
       const spawn = this.origOwner.canBuild(
         UnitType.TradeShip,
         this.srcPort.tile(),
       );
-      if (spawn == false) {
+      if (spawn === false) {
         consolex.warn(`cannot build trade ship`);
         this.active = false;
         return;
@@ -55,14 +58,14 @@ export class TradeShipExecution implements Execution {
       return;
     }
 
-    if (this.origOwner != this.tradeShip.owner()) {
+    if (this.origOwner !== this.tradeShip.owner()) {
       // Store as vairable in case ship is recaptured by previous owner
       this.wasCaptured = true;
     }
 
     // If a player captures an other player's port while trading we should delete
     // the ship.
-    if (this._dstPort.owner().id() == this.srcPort.owner().id()) {
+    if (this._dstPort.owner().id() === this.srcPort.owner().id()) {
       this.tradeShip.delete(false);
       this.active = false;
       return;
@@ -83,7 +86,7 @@ export class TradeShipExecution implements Execution {
         .owner()
         .units(UnitType.Port)
         .sort(distSortUnit(this.mg, this.tradeShip));
-      if (ports.length == 0) {
+      if (ports.length === 0) {
         this.tradeShip.delete(false);
         this.active = false;
         return;
@@ -120,6 +123,10 @@ export class TradeShipExecution implements Execution {
   }
 
   private complete() {
+    if (this.mg === null || this.origOwner === null) {
+      throw new Error("Not initialized");
+    }
+    if (this.tradeShip === null) return;
     this.active = false;
     this.tradeShip.delete(false);
     const gold = this.mg