diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 468d6aac14b..9d086e4549e 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -135,7 +135,7 @@ namespace ts.projectSystem {
     }
 
     export class TestServerEventManager {
-        private events: server.ProjectServiceEvent[] = [];
+        public events: server.ProjectServiceEvent[] = [];
 
         handler: server.ProjectServiceEventHandler = (event: server.ProjectServiceEvent) => {
             this.events.push(event);
@@ -2286,6 +2286,14 @@ namespace ts.projectSystem {
             const session = createSession(host, /*typingsInstaller*/ undefined, serverEventManager.handler);
             openFilesForSession([file], session);
             serverEventManager.checkEventCountOfType("configFileDiag", 1);
+
+            for (const event of serverEventManager.events) {
+                if (event.eventName === "configFileDiag") {
+                    assert.equal(event.data.configFileName, configFile.path);
+                    assert.equal(event.data.triggerFile, file.path);
+                    return;
+                }
+            }
         });
 
         it("are generated when the config file doesn't have errors", () => {
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 91b9f90c88b..54b257242fd 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -11,7 +11,7 @@ namespace ts.server {
     export const maxProgramSizeForNonTsFiles = 20 * 1024 * 1024;
 
     export type ProjectServiceEvent =
-        { eventName: "context", data: { project: Project, fileName: NormalizedPath } } | { eventName: "configFileDiag", data: { triggerFile?: string, configFileName: string, diagnostics: Diagnostic[] } };
+        { eventName: "context", data: { project: Project, fileName: NormalizedPath } } | { eventName: "configFileDiag", data: { triggerFile: string, configFileName: string, diagnostics: Diagnostic[] } };
 
     export interface ProjectServiceEventHandler {
         (event: ProjectServiceEvent): void;
@@ -392,12 +392,12 @@ namespace ts.server {
             this.throttledOperations.schedule(
                 project.configFileName,
                 /*delay*/250,
-                () => this.handleChangeInSourceFileForConfiguredProject(project));
+                () => this.handleChangeInSourceFileForConfiguredProject(project, fileName));
         }
 
-        private handleChangeInSourceFileForConfiguredProject(project: ConfiguredProject) {
+        private handleChangeInSourceFileForConfiguredProject(project: ConfiguredProject, triggerFile: string) {
             const { projectOptions, configFileErrors } = this.convertConfigFileContentToProjectOptions(project.configFileName);
-            this.reportConfigFileDiagnostics(project.getProjectName(), configFileErrors);
+            this.reportConfigFileDiagnostics(project.getProjectName(), configFileErrors, triggerFile);
 
             const newRootFiles = projectOptions.files.map((f => this.getCanonicalFileName(f)));
             const currentRootFiles = project.getRootFiles().map((f => this.getCanonicalFileName(f)));
@@ -434,7 +434,7 @@ namespace ts.server {
             }
 
             const { configFileErrors } = this.convertConfigFileContentToProjectOptions(fileName);
-            this.reportConfigFileDiagnostics(fileName, configFileErrors);
+            this.reportConfigFileDiagnostics(fileName, configFileErrors, fileName);
 
             this.logger.info(`Detected newly added tsconfig file: ${fileName}`);
             this.reloadProjects();
@@ -757,7 +757,7 @@ namespace ts.server {
             return project;
         }
 
-        private reportConfigFileDiagnostics(configFileName: string, diagnostics: Diagnostic[], triggerFile?: string) {
+        private reportConfigFileDiagnostics(configFileName: string, diagnostics: Diagnostic[], triggerFile: string) {
             if (!this.eventHandler) {
                 return;
             }
diff --git a/src/server/session.ts b/src/server/session.ts
index 539142eff18..3df6a1acb51 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -761,7 +761,7 @@ namespace ts.server {
             if (this.eventHander) {
                 this.eventHander({
                     eventName: "configFileDiag",
-                    data: { fileName, configFileName, diagnostics: configFileErrors || [] }
+                    data: { triggerFile: fileName, configFileName, diagnostics: configFileErrors || [] }
                 });
             }
         }