diff --git a/src/server/IPCBridgeSchema.ts b/src/server/IPCBridgeSchema.ts
index 48293614d..4ac8c1531 100644
--- a/src/server/IPCBridgeSchema.ts
+++ b/src/server/IPCBridgeSchema.ts
@@ -1,7 +1,6 @@
 import { z } from "zod";
 import {
   GameConfigSchema,
-  PublicGameInfoSchema,
   PublicGamesSchema,
   PublicGameTypeSchema,
 } from "../core/Schemas";
@@ -19,10 +18,14 @@ export type MasterMessage = z.infer<typeof MasterMessageSchema>;
 
 // --- Worker Messages ---
 
-// Worker tells the master about its lobbies.
+// Worker tells the master about its lobbies. Entries are deliberately not
+// validated here: the master checks each against PublicGameInfoSchema and
+// drops bad ones (MasterLobbyService.validLobbies), so a single malformed
+// lobby can't invalidate the whole report and freeze the master's view of
+// this worker's lobbies.
 const WorkerLobbyListSchema = z.object({
   type: z.literal("lobbyList"),
-  lobbies: z.array(PublicGameInfoSchema),
+  lobbies: z.array(z.unknown()),
 });
 
 const WorkerReadySchema = z.object({
diff --git a/src/server/MasterLobbyService.ts b/src/server/MasterLobbyService.ts
index 25e4d23df..603b76cd9 100644
--- a/src/server/MasterLobbyService.ts
+++ b/src/server/MasterLobbyService.ts
@@ -1,6 +1,10 @@
 import { Worker } from "cluster";
 import winston from "winston";
-import { PublicGameInfo, PublicGameType } from "../core/Schemas";
+import {
+  PublicGameInfo,
+  PublicGameInfoSchema,
+  PublicGameType,
+} from "../core/Schemas";
 import { generateID } from "../core/Util";
 import {
   MasterCreateGame,
@@ -46,12 +50,30 @@ export class MasterLobbyService {
           this.handleWorkerReady(msg.workerId);
           break;
         case "lobbyList":
-          this.workerLobbies.set(workerId, msg.lobbies);
+          this.workerLobbies.set(workerId, this.validLobbies(msg.lobbies));
           break;
       }
     });
   }
 
+  // Lobby entries are validated individually so one malformed entry only
+  // drops itself. Rejecting the whole report would freeze this worker's
+  // lobbies in the master's view for as long as the bad entry exists —
+  // stale broadcasts to every client, countdown resets, and duplicate
+  // scheduling.
+  private validLobbies(lobbies: unknown[]): PublicGameInfo[] {
+    const valid: PublicGameInfo[] = [];
+    for (const lobby of lobbies) {
+      const result = PublicGameInfoSchema.safeParse(lobby);
+      if (result.success) {
+        valid.push(result.data);
+      } else {
+        this.log.error("Dropping invalid lobby in worker report:", lobby);
+      }
+    }
+    return valid;
+  }
+
   removeWorker(workerId: number) {
     this.workers.delete(workerId);
     this.workerLobbies.delete(workerId);
diff --git a/src/server/WorkerLobbyService.ts b/src/server/WorkerLobbyService.ts
index 6e7f405a1..c84776269 100644
--- a/src/server/WorkerLobbyService.ts
+++ b/src/server/WorkerLobbyService.ts
@@ -98,9 +98,13 @@ export class WorkerLobbyService {
   }
 
   private sendMyLobbiesToMaster() {
+    // Matchmaking games have a Public gameType (so they appear in
+    // publicLobbies()) but no publicGameType: they are invite-only and must
+    // never be advertised, and the master rejects entries without one.
     const lobbies = this.gm
       .publicLobbies()
       .map((g) => g.gameInfo())
+      .filter((gi) => gi.publicGameType !== undefined)
       .map((gi) => {
         return {
           gameID: gi.gameID,
diff --git a/tests/server/MasterLobbyServiceHealth.test.ts b/tests/server/MasterLobbyServiceHealth.test.ts
index d29fcce75..386f32959 100644
--- a/tests/server/MasterLobbyServiceHealth.test.ts
+++ b/tests/server/MasterLobbyServiceHealth.test.ts
@@ -48,6 +48,33 @@ function startAllWorkers(
   return workers;
 }
 
+describe("MasterLobbyService lobby report validation", () => {
+  it("keeps the valid lobbies when a report contains a malformed entry", () => {
+    const service = createService(1);
+    const [{ w }] = startAllWorkers(service, 1);
+
+    w.emit("message", {
+      type: "lobbyList",
+      lobbies: [
+        // Missing publicGameType, like a matchmaking game reported by
+        // mistake. It must be dropped without discarding the whole report.
+        { gameID: "bad", numClients: 0 },
+        { gameID: "good", numClients: 1, publicGameType: "ffa" },
+      ],
+    });
+
+    (service as any).broadcastLobbies();
+
+    const broadcast = ((w as any).send as ReturnType<typeof vi.fn>).mock.calls
+      .map((c) => c[0])
+      .find((m) => m.type === "lobbiesBroadcast");
+    expect(broadcast).toBeDefined();
+    expect(
+      broadcast.publicGames.games.ffa.map((l: { gameID: string }) => l.gameID),
+    ).toEqual(["good"]);
+  });
+});
+
 describe("MasterLobbyService.isHealthy", () => {
   it("unhealthy before any workers register", () => {
     const service = createService(4);