diff --git a/packages/controller/src/HostConnection.ts b/packages/controller/src/HostConnection.ts
index ec2f55d9..5bbc59e2 100644
--- a/packages/controller/src/HostConnection.ts
+++ b/packages/controller/src/HostConnection.ts
@@ -18,6 +18,8 @@ import HostRecord from "./HostRecord.js";
 export default class HostConnection extends BaseConnection {
 	private info: HostRecord;
 	plugins: Map<string, string>;
+	// Warn once per connection, a misbehaving host could log in a loop.
+	private _warnedBogusLogMessage = false;
 
 	constructor(
 		registerData: lib.RegisterHostData,
@@ -295,20 +297,22 @@ export default class HostConnection extends BaseConnection {
 		await this.send(new lib.SyncUserListsEvent(adminlist, banlist, whitelist));
 	}
 
-	async handleInstanceSaveDetailsUpdatesEvent(event: lib.InstanceSaveDetailsUpdatesEvent) {
-		// A host may only report saves for instances assigned to it. Otherwise
-		// any host could inject save records for, or wipe the save list of, an
-		// instance on a different host. See handleInstanceStatusChangedEvent.
-		const assignedHere = (instanceId: number) => {
-			const instance = this._controller.instances.get(instanceId);
-			return instance !== undefined && instance.config.get("instance.assigned_host") === this.id;
-		};
+	// A host may only report on instances assigned to it. Otherwise any host
+	// could speak for an instance on a different host. See
+	// handleInstanceStatusChangedEvent.
+	private _assignedHere(instanceId: number) {
+		const instance = this._controller.instances.get(instanceId);
+		return instance !== undefined && instance.config.get("instance.assigned_host") === this.id;
+	}
 
-		if (event.instanceId !== undefined && !assignedHere(event.instanceId)) {
+	async handleInstanceSaveDetailsUpdatesEvent(event: lib.InstanceSaveDetailsUpdatesEvent) {
+		// Otherwise any host could inject save records for, or wipe the save
+		// list of, an instance on a different host.
+		if (event.instanceId !== undefined && !this._assignedHere(event.instanceId)) {
 			logger.warn(`Got bogus save updates for instance id ${event.instanceId}`);
 			return;
 		}
-		if (event.updates.some(save => !assignedHere(save.instanceId))) {
+		if (event.updates.some(save => !this._assignedHere(save.instanceId))) {
 			logger.warn(`Got bogus save updates from host id ${this.id}`);
 			return;
 		}
@@ -337,8 +341,23 @@ export default class HostConnection extends BaseConnection {
 	}
 
 	async handleLogMessageEvent(event: lib.LogMessageEvent) {
+		// Fields beyond level and message survive schema validation, so the
+		// instance a log line claims to come from is whatever the host sent.
+		const info: typeof event.info & { instance_id?: number, instance_name?: string } = { ...event.info };
+		if (info.instance_id !== undefined && !this._assignedHere(info.instance_id)) {
+			// Demote to a host level line instead of dropping it. The host did
+			// log this, it just does not get to pin it on someone else's
+			// instance, and a host racing a reassignment still gets heard.
+			if (!this._warnedBogusLogMessage) {
+				this._warnedBogusLogMessage = true;
+				logger.warn(`Got bogus log message for instance id ${info.instance_id}`);
+			}
+			delete info.instance_id;
+			delete info.instance_name;
+		}
+
 		this._controller.clusterLogger.log({
-			...event.info,
+			...info,
 			host_id: this.id,
 			host_name: this.info.name,
 		});
diff --git a/test/controller/HostConnection.test.js b/test/controller/HostConnection.test.js
index fde949d9..fe884c98 100644
--- a/test/controller/HostConnection.test.js
+++ b/test/controller/HostConnection.test.js
@@ -39,13 +39,14 @@ describe("controller/src/HostConnection", function() {
 		// Instance 1 is on host 10, instance 2 is on host 20.
 		const assignments = new Map([[1, 10], [2, 20]]);
 
+		// Inherit the prototype, handlers call other methods on this.
 		function run(hostId, saves, event) {
 			const saveStore = new MockSaves(saves);
-			const ctx = {
-				id: hostId,
+			const ctx = Object.assign(Object.create(HostConnection.prototype), {
+				info: { id: hostId },
 				_controller: { instances: makeInstances(assignments), saves: saveStore },
-			};
-			HostConnection.prototype.handleInstanceSaveDetailsUpdatesEvent.call(ctx, event);
+			});
+			ctx.handleInstanceSaveDetailsUpdatesEvent(event);
 			return saveStore;
 		}
 
@@ -75,4 +76,50 @@ describe("controller/src/HostConnection", function() {
 			assert.deepEqual([...store.values()], []);
 		});
 	});
+
+	describe(".handleLogMessageEvent()", function() {
+		// Instance 1 is on host 10, instance 2 is on host 20.
+		const assignments = new Map([[1, 10], [2, 20]]);
+
+		function run(hostId, info) {
+			const logged = [];
+			const ctx = Object.assign(Object.create(HostConnection.prototype), {
+				info: { id: hostId, name: `host-${hostId}` },
+				_controller: {
+					instances: makeInstances(assignments),
+					clusterLogger: { log(entry) { logged.push(entry); } },
+				},
+			});
+			ctx.handleLogMessageEvent(new lib.LogMessageEvent(info));
+			return logged;
+		}
+
+		it("keeps instance fields for an instance assigned to this host", async function() {
+			const logged = run(10, { level: "info", message: "hello", instance_id: 1, instance_name: "one" });
+			assert.deepEqual(logged, [{
+				level: "info", message: "hello", instance_id: 1, instance_name: "one",
+				host_id: 10, host_name: "host-10",
+			}]);
+		});
+
+		it("logs host level messages unchanged", async function() {
+			const logged = run(10, { level: "info", message: "hello" });
+			assert.deepEqual(logged, [{ level: "info", message: "hello", host_id: 10, host_name: "host-10" }]);
+		});
+
+		it("strips instance fields claiming an instance on another host", async function() {
+			const logged = run(30, { level: "info", message: "hi", instance_id: 1, instance_name: "one" });
+			assert.deepEqual(logged, [{ level: "info", message: "hi", host_id: 30, host_name: "host-30" }]);
+		});
+
+		it("strips instance fields claiming a nonexistent instance", async function() {
+			const logged = run(30, { level: "info", message: "hi", instance_id: 999, instance_name: "ghost" });
+			assert.deepEqual(logged, [{ level: "info", message: "hi", host_id: 30, host_name: "host-30" }]);
+		});
+
+		it("overrides host fields sent by the host", async function() {
+			const logged = run(10, { level: "info", message: "hi", host_id: 99, host_name: "spoofed" });
+			assert.deepEqual(logged, [{ level: "info", message: "hi", host_id: 10, host_name: "host-10" }]);
+		});
+	});
 });