diff --git a/src/server/session.ts b/src/server/session.ts
index a3598478655..f08d809a171 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -1453,9 +1453,9 @@ namespace ts.server {
         }
 
         private provideInlayHints(args: protocol.InlayHintsRequestArgs) {
-            const { file, languageService } = this.getFileAndLanguageServiceForSyntacticOperation(args);
+            const { file, project } = this.getFileAndProject(args);
             const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
-            const hints = languageService.provideInlayHints(file, args, this.getPreferences(file));
+            const hints = project.getLanguageService().provideInlayHints(file, args, this.getPreferences(file));
 
             return hints.map(hint => ({
                 ...hint,
diff --git a/src/testRunner/tsconfig.json b/src/testRunner/tsconfig.json
index e4274fabe1b..d5aa42ef79b 100644
--- a/src/testRunner/tsconfig.json
+++ b/src/testRunner/tsconfig.json
@@ -191,6 +191,7 @@
         "unittests/tsserver/getExportReferences.ts",
         "unittests/tsserver/getFileReferences.ts",
         "unittests/tsserver/importHelpers.ts",
+        "unittests/tsserver/inlayHints.ts",
         "unittests/tsserver/inferredProjects.ts",
         "unittests/tsserver/jsdocTag.ts",
         "unittests/tsserver/languageService.ts",
diff --git a/src/testRunner/unittests/tsserver/inlayHints.ts b/src/testRunner/unittests/tsserver/inlayHints.ts
new file mode 100644
index 00000000000..837bc9c452e
--- /dev/null
+++ b/src/testRunner/unittests/tsserver/inlayHints.ts
@@ -0,0 +1,63 @@
+namespace ts.projectSystem {
+    describe("unittests:: tsserver:: inlayHints", () => {
+        const configFile: File = {
+            path: "/a/b/tsconfig.json",
+            content: "{}"
+        };
+        const app: File = {
+            path: "/a/b/app.ts",
+            content: "declare function foo(param: any): void;\nfoo(12);"
+        };
+
+        it("with updateOpen request does not corrupt documents", () => {
+            const host = createServerHost([app, commonFile1, commonFile2, libFile, configFile]);
+            const session = createSession(host);
+            session.executeCommandSeq<protocol.OpenRequest>({
+                command: protocol.CommandTypes.Open,
+                arguments: { file: app.path }
+            });
+            session.executeCommandSeq<protocol.ConfigureRequest>({
+                command: protocol.CommandTypes.Configure,
+                arguments: {
+                    preferences: {
+                        includeInlayParameterNameHints: "all"
+                    } as UserPreferences
+                }
+            });
+            verifyInlayHintResponse(session);
+            session.executeCommandSeq<protocol.UpdateOpenRequest>({
+                command: protocol.CommandTypes.UpdateOpen,
+                arguments: {
+                    changedFiles: [{ fileName: app.path, textChanges: [{ start: { line: 1, offset: 39 }, end: { line: 1, offset: 39 }, newText: "//" }] }]
+                }
+            });
+            verifyInlayHintResponse(session);
+            session.executeCommandSeq<protocol.UpdateOpenRequest>({
+                command: protocol.CommandTypes.UpdateOpen,
+                arguments: {
+                    changedFiles: [{ fileName: app.path, textChanges: [{ start: { line: 1, offset: 41 }, end: { line: 1, offset: 41 }, newText: "c" }] }]
+                }
+            });
+            verifyInlayHintResponse(session);
+
+            function verifyInlayHintResponse(session: TestSession) {
+                verifyParamInlayHint(session.executeCommandSeq<protocol.InlayHintsRequest>({
+                    command: protocol.CommandTypes.ProvideInlayHints,
+                    arguments: {
+                        file: app.path,
+                        start: 0,
+                        length: app.content.length,
+                    }
+                }).response as protocol.InlayHintItem[] | undefined);
+            }
+
+            function verifyParamInlayHint(response: protocol.InlayHintItem[] | undefined) {
+                Debug.assert(response);
+                Debug.assert(response[0]);
+                Debug.assertEqual(response[0].text, "param:");
+                Debug.assertEqual(response[0].position.line, 2);
+                Debug.assertEqual(response[0].position.offset, 5);
+            }
+        });
+    });
+}