diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index 5da61fd542a..a210349c146 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -698,7 +698,8 @@ namespace Harness.LanguageService {
                 /*useOneInferredProject*/ false,
                 /*typingsInstaller*/ undefined,
                 Utils.byteLength,
-                process.hrtime, serverHost);
+                process.hrtime, serverHost,
+                /*canUseEvents*/ true);
 
             // Fake the connection between the client and the server
             serverHost.writeMessage = client.onMessage.bind(client);
diff --git a/src/harness/unittests/session.ts b/src/harness/unittests/session.ts
index 0d1fb3681e0..abfac4b082d 100644
--- a/src/harness/unittests/session.ts
+++ b/src/harness/unittests/session.ts
@@ -44,7 +44,7 @@ namespace ts.server {
         let lastSent: protocol.Message;
 
         beforeEach(() => {
-            session = new Session(mockHost, nullCancellationToken, /*useOneInferredProject*/ false, /*typingsInstaller*/ undefined, Utils.byteLength, process.hrtime, mockLogger);
+            session = new Session(mockHost, nullCancellationToken, /*useOneInferredProject*/ false, /*typingsInstaller*/ undefined, Utils.byteLength, process.hrtime, mockLogger, /*canUseEvents*/ true);
             session.send = (msg: protocol.Message) => {
                 lastSent = msg;
             };
@@ -269,7 +269,7 @@ namespace ts.server {
             lastSent: protocol.Message;
             customHandler = "testhandler";
             constructor() {
-                super(mockHost, nullCancellationToken, /*useOneInferredProject*/ false, /*typingsInstaller*/ undefined, Utils.byteLength, process.hrtime, mockLogger);
+                super(mockHost, nullCancellationToken, /*useOneInferredProject*/ false, /*typingsInstaller*/ undefined, Utils.byteLength, process.hrtime, mockLogger, /*canUseEvents*/ true);
                 this.addProtocolHandler(this.customHandler, () => {
                     return { response: undefined, responseRequired: true };
                 });
@@ -327,7 +327,7 @@ namespace ts.server {
         class InProcSession extends Session {
             private queue: protocol.Request[] = [];
             constructor(private client: InProcClient) {
-                super(mockHost, nullCancellationToken, /*useOneInferredProject*/ false, /*typingsInstaller*/ undefined, Utils.byteLength, process.hrtime, mockLogger);
+                super(mockHost, nullCancellationToken, /*useOneInferredProject*/ false, /*typingsInstaller*/ undefined, Utils.byteLength, process.hrtime, mockLogger, /*canUseEvents*/ true);
                 this.addProtocolHandler("echo", (req: protocol.Request) => ({
                     response: req.arguments,
                     responseRequired: true
diff --git a/src/server/server.ts b/src/server/server.ts
index b52db6f517e..11cc4b94740 100644
--- a/src/server/server.ts
+++ b/src/server/server.ts
@@ -232,8 +232,22 @@ namespace ts.server {
     }
 
     class IOSession extends Session {
-        constructor(host: ServerHost, cancellationToken: HostCancellationToken, eventPort: number, useSingleInferredProject: boolean, logger: server.Logger) {
-            super(host, cancellationToken, useSingleInferredProject, new NodeTypingsInstaller(logger, eventPort, host.newLine), Buffer.byteLength, process.hrtime, logger);
+        constructor(
+            host: ServerHost,
+            cancellationToken: HostCancellationToken,
+            installerEventPort: number,
+            canUseEvents: boolean,
+            useSingleInferredProject: boolean,
+            logger: server.Logger) {
+            super(
+                host,
+                cancellationToken,
+                useSingleInferredProject,
+                new NodeTypingsInstaller(logger, installerEventPort, host.newLine),
+                Buffer.byteLength,
+                process.hrtime,
+                logger,
+                canUseEvents);
         }
 
         exit() {
@@ -477,7 +491,7 @@ namespace ts.server {
     }
 
     const useSingleInferredProject = sys.args.indexOf("--useSingleInferredProject") >= 0;
-    const ioSession = new IOSession(sys, cancellationToken, eventPort, useSingleInferredProject, logger);
+    const ioSession = new IOSession(sys, cancellationToken, eventPort, /*canUseEvents*/ eventPort === undefined, useSingleInferredProject, logger);
     process.on("uncaughtException", function (err: Error) {
         ioSession.logError(err, "unknown");
     });
diff --git a/src/server/session.ts b/src/server/session.ts
index 860e90a1a57..5ae7307737e 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -158,11 +158,14 @@ namespace ts.server {
             protected readonly typingsInstaller: ITypingsInstaller,
             private byteLength: (buf: string, encoding?: string) => number,
             private hrtime: (start?: number[]) => number[],
-            protected logger: Logger) {
-            this.projectService =
-                new ProjectService(host, logger, cancellationToken, useSingleInferredProject, typingsInstaller, (eventName, project, fileName) => {
-                    this.handleEvent(eventName, project, fileName);
-                });
+            protected logger: Logger,
+            protected readonly canUseEvents: boolean) {
+
+            const eventHandler: ProjectServiceEventHandler = canUseEvents
+                ? (eventName, project, fileName) => this.handleEvent(eventName, project, fileName)
+                : undefined;
+
+            this.projectService = new ProjectService(host, logger, cancellationToken, useSingleInferredProject, typingsInstaller, eventHandler);
             this.gcTimer = new GcTimer(host, /*delay*/ 15000, logger);
         }
 
@@ -186,6 +189,12 @@ namespace ts.server {
         }
 
         public send(msg: protocol.Message) {
+            if (msg.type === "event" && !this.canUseEvents) {
+                if (this.logger.hasLevel(LogLevel.verbose)) {
+                    this.logger.info(`Session does not support events: ignored event: ${JSON.stringify(msg)}`);
+                }
+                return;
+            }
             this.host.write(formatMessage(msg, this.logger, this.byteLength, this.host.newLine));
         }