diff --git a/frontend/angular/src/app/features/host/host-shell.component.ts b/frontend/angular/src/app/features/host/host-shell.component.ts
index 59087b0..4253051 100644
--- a/frontend/angular/src/app/features/host/host-shell.component.ts
+++ b/frontend/angular/src/app/features/host/host-shell.component.ts
@@ -156,7 +156,7 @@ export class HostShellComponent implements OnInit, OnDestroy {
     try {
       const state = await this.controller.hydrateLobby(this.sessionCode);
       if (!state.session || state.errorMessage) {
-        throw new Error(state.errorMessage ?? 'Unknown error');
+        throw new Error(state.errorMessage ?? this.copy('common.unknown_error'));
       }
       this.session = state.session as SessionDetail;
       this.sessionCode = this.session.session.code;
@@ -177,7 +177,7 @@ export class HostShellComponent implements OnInit, OnDestroy {
     await this.runAction(async () => {
       const state = await this.controller.startRound(this.sessionCode, this.categorySlug.trim());
       if (!state.session || state.errorMessage) {
-        throw new Error(state.errorMessage ?? 'Unknown error');
+        throw new Error(state.errorMessage ?? this.copy('common.unknown_error'));
       }
       this.session = state.session as SessionDetail;
       this.sessionCode = this.session.session.code;
diff --git a/frontend/angular/src/app/features/player/player-shell.component.ts b/frontend/angular/src/app/features/player/player-shell.component.ts
index 2bbc9f4..aa5fdcb 100644
--- a/frontend/angular/src/app/features/player/player-shell.component.ts
+++ b/frontend/angular/src/app/features/player/player-shell.component.ts
@@ -433,7 +433,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     try {
       const state = await this.controller.hydrateLobby(this.sessionCode);
       if (!state.session || state.errorMessage) {
-        throw new Error(state.errorMessage ?? 'Unknown error');
+        throw new Error(state.errorMessage ?? this.copy('common.unknown_error'));
       }
       this.session = state.session as SessionDetail;
       this.sessionCode = this.session.session.code;
@@ -459,7 +459,7 @@ export class PlayerShellComponent implements OnInit, OnDestroy {
     try {
       const state = await this.controller.joinLobby(this.sessionCode, this.nickname);
       if (!state.session || state.errorMessage) {
-        throw new Error(state.errorMessage ?? 'Unknown error');
+        throw new Error(state.errorMessage ?? this.copy('common.unknown_error'));
       }
       this.session = state.session as SessionDetail;
       this.sessionCode = this.session.session.code;