diff --git a/plugins/player_sync/test/controller.js b/plugins/player_sync/test/controller.js
index d87c437e..ec2771d6 100644
--- a/plugins/player_sync/test/controller.js
+++ b/plugins/player_sync/test/controller.js
@@ -6,7 +6,7 @@ import * as lib from "@clusterio/lib";
 import * as mock from "../../../test/mock.js";
 import controllerEntrypoint from "../dist/node/controller.js";
 import { plugin as info } from "../dist/node/index.js";
-import { DatabaseStatsRequest } from "../dist/node/messages.js";
+import { DatabaseStatsRequest, DownloadRequest, UploadRequest } from "../dist/node/messages.js";
 
 describe("player_sync controller", function() {
 	const databaseDir = path.join("temp", "test", "player_sync");
@@ -50,4 +50,41 @@ describe("player_sync controller", function() {
 		assert.equal(stats.databaseEntries, 1);
 		assert.equal(stats.largestEntry.name, "new");
 	});
+
+	describe("UploadRequest", function() {
+		let controller;
+		let disabled;
+		beforeEach(async function() {
+			disabled = [];
+			const stored = { generation: 1, name: "test", force: "player", tag: "stored" };
+			await fs.writeFile(path.join(databaseDir, "player_sync.json"), JSON.stringify([["test", stored]]));
+			controller = await load();
+			controller.instances = new Map([[1, {
+				config: {
+					get: name => {
+						if (name === "instance.name") { return "test instance"; }
+						return !disabled.includes(name.replace("player_sync.sync_", ""));
+					},
+				},
+			}]]);
+		});
+
+		async function upload(playerData) {
+			await mock.getHandler(controller, UploadRequest)({ instanceId: 1, playerName: "test", playerData });
+			return (await mock.getHandler(controller, DownloadRequest)({ instanceId: 1, playerName: "test" }))
+				.playerData;
+		}
+
+		it("should store the upload as is when everything is synced", async function() {
+			const playerData = { generation: 2, name: "test", force: "enemy", tag: "uploaded" };
+			assert.deepEqual(await upload(playerData), playerData);
+		});
+		it("should keep stored fields the uploading instance does not sync", async function() {
+			disabled = ["force"];
+			assert.deepEqual(
+				await upload({ generation: 2, name: "test", tag: "uploaded" }),
+				{ generation: 2, name: "test", force: "player", tag: "uploaded" },
+			);
+		});
+	});
 });