diff --git a/packages/controller/src/HostConnection.ts b/packages/controller/src/HostConnection.ts
index 72185d37..164f3e82 100644
--- a/packages/controller/src/HostConnection.ts
+++ b/packages/controller/src/HostConnection.ts
@@ -269,12 +269,14 @@ export default class HostConnection extends BaseConnection {
 	}
 
 	async handleInstanceSaveDetailsUpdatesEvent(event: lib.InstanceSaveDetailsUpdatesEvent) {
+		const now = Date.now();
 		const updates: lib.SaveDetails[] = [];
 		for (const save of event.updates) {
 			const existingSave = this._controller.saves.get(save.id);
 			if (existingSave && save.equals(existingSave)) {
 				continue;
 			}
+			save.updatedAt = now;
 			this._controller.saves.set(save.id, save);
 			updates.push(save);
 		}
@@ -283,6 +285,7 @@ export default class HostConnection extends BaseConnection {
 			for (const [id, save] of this._controller.saves) {
 				if (save.instanceId === event.instanceId && !updatedSaves.has(id)) {
 					save.isDeleted = true;
+					save.updatedAt = now;
 					updates.push(save);
 					this._controller.saves.delete(id);
 				}
diff --git a/packages/host/src/Instance.ts b/packages/host/src/Instance.ts
index c49b3035..22c43cf7 100644
--- a/packages/host/src/Instance.ts
+++ b/packages/host/src/Instance.ts
@@ -402,6 +402,7 @@ rcon.print(game.table_to_json(players))`.replace(/\r?\n/g, " ");
 				stat.mtimeMs,
 				name === loadedSave,
 				name === defaultSave,
+				0, // Set by controller
 				false,
 			));
 		}
diff --git a/packages/lib/src/data/messages_instance.ts b/packages/lib/src/data/messages_instance.ts
index 17a27adf..dbc32be1 100644
--- a/packages/lib/src/data/messages_instance.ts
+++ b/packages/lib/src/data/messages_instance.ts
@@ -290,6 +290,8 @@ export class SaveDetails {
 		public mtimeMs: number,
 		public loaded: boolean,
 		public loadByDefault: boolean,
+		/** Millisecond Unix timestamp this entry was last updated at */
+		public updatedAt: number,
 		public isDeleted: boolean,
 	) { }
 
@@ -301,6 +303,7 @@ export class SaveDetails {
 		"mtimeMs": Type.Number(),
 		"loaded": Type.Boolean(),
 		"loadByDefault": Type.Boolean(),
+		"updatedAt": Type.Number(),
 		"isDeleted": Type.Boolean(),
 	});
 
@@ -313,6 +316,7 @@ export class SaveDetails {
 			json.mtimeMs,
 			json.loaded,
 			json.loadByDefault,
+			json.updatedAt,
 			json.isDeleted,
 		);
 	}
@@ -322,16 +326,16 @@ export class SaveDetails {
 		return `${this.instanceId}/${this.name}`;
 	}
 
-	get updatedAt() {
-		return this.mtimeMs;
-	}
-
 	/**
 	 * Compare this save with another save.
 	 * @param other - save to compare with.
 	 * @returns true if this save is identical to the provided save
 	 */
 	equals(other: SaveDetails) {
+		// Note that updatedAt is not included in the equality check because
+		// instances send the whole list of saves with updatedAt set to zero
+		// to the controller whenever any save changes and this equals check
+		// is used to filter whether a save was updated.
 		return (
 			this.instanceId === other.instanceId
 			&& this.type === other.type