diff --git a/arduino-ide-extension/src/browser/monitor-manager-proxy-client-impl.ts b/arduino-ide-extension/src/browser/monitor-manager-proxy-client-impl.ts
index 45956ce5..76425a4e 100644
--- a/arduino-ide-extension/src/browser/monitor-manager-proxy-client-impl.ts
+++ b/arduino-ide-extension/src/browser/monitor-manager-proxy-client-impl.ts
@@ -1,6 +1,6 @@
 import { Emitter } from "@theia/core";
 import { injectable } from "@theia/core/shared/inversify";
-import { MonitorManagerProxyClient } from "../common/monitor-manager-proxy";
+import { MonitorManagerProxyClient } from "../common/protocol/monitor-service";
 
 @injectable()
 export class MonitorManagerProxyClientImpl implements MonitorManagerProxyClient {
diff --git a/arduino-ide-extension/src/common/protocol/monitor-service.ts b/arduino-ide-extension/src/common/protocol/monitor-service.ts
index d3d5c1ed..0847068c 100644
--- a/arduino-ide-extension/src/common/protocol/monitor-service.ts
+++ b/arduino-ide-extension/src/common/protocol/monitor-service.ts
@@ -10,8 +10,8 @@ export interface MonitorManagerProxy extends JsonRpcServer<MonitorManagerProxyCl
 
 export const MonitorManagerProxyClient = Symbol('MonitorManagerProxyClient');
 export interface MonitorManagerProxyClient {
-    onWebSocketChanged: Event<string>;
-    notifyWebSocketChanged(message: string): void;
+    onWebSocketChanged: Event<number>;
+    notifyWebSocketChanged(message: number): void;
 }
 
 export interface MonitorSetting {