diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 362b477c80f..46f84a39af3 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -2183,7 +2183,7 @@ namespace ts {
                 for (let i = 0; i < errors.length; i++) {
                     const actualMessage = flattenDiagnosticMessageText(errors[i].messageText, "\n");
                     const expectedMessage = expectedErrors[i];
-                    assert.equal(actualMessage, expectedMessage, "error message does not match");
+                    assert.isTrue(actualMessage.indexOf(expectedMessage) === 0, `error message does not match, expected ${actualMessage} to start with ${expectedMessage}`);
                 }
             }
         }
@@ -2297,7 +2297,7 @@ namespace ts {
                     "')' expected.",
                     "Declaration or statement expected.",
                     "Declaration or statement expected.",
-                    "Failed to parse file '/a/b/tsconfig.json': Unexpected token ) in JSON at position 7."
+                    "Failed to parse file '/a/b/tsconfig.json'"
                 ]);
             }
             // fix config and trigger watcher
@@ -2349,7 +2349,7 @@ namespace ts {
                     "')' expected.",
                     "Declaration or statement expected.",
                     "Declaration or statement expected.",
-                    "Failed to parse file '/a/b/tsconfig.json': Unexpected token ) in JSON at position 7."
+                    "Failed to parse file '/a/b/tsconfig.json'"
                 ]);
             }
         });
@@ -2375,4 +2375,27 @@ namespace ts {
             checkProjectRootFiles(project, [file1.path]);
         });
     });
+
+    describe("autoDiscovery", () => {
+        it("does not depend on extension", () => {
+            const file1 = {
+                path: "/a/b/app.html",
+                content: ""
+            };
+            const file2 = {
+                path: "/a/b/app.d.ts",
+                content: ""
+            };
+            const host = createServerHost([file1, file2]);
+            const projectService = createProjectService(host);
+            projectService.openExternalProject({
+                projectFileName: "/a/b/proj.csproj",
+                rootFiles: [toExternalFile(file2.path), { fileName: file1.path, hasMixedContent: true, scriptKind: ScriptKind.JS }],
+                options: {}
+            });
+            projectService.checkNumberOfProjects({ externalProjects: 1 });
+            const typingOptions = projectService.externalProjects[0].getTypingOptions();
+            assert.isTrue(typingOptions.enableAutoDiscovery, "Typing autodiscovery should be enabled");
+        });
+    });
 }
\ No newline at end of file
diff --git a/src/server/project.ts b/src/server/project.ts
index 4adbc7ca059..6700b906179 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -20,10 +20,10 @@ namespace ts.server {
         }
     }
 
-    const jsOrDts = [".js", ".d.ts"];
-
     export function allRootFilesAreJsOrDts(project: Project): boolean {
-        return project.getRootScriptInfos().every(f => fileExtensionIsAny(f.fileName, jsOrDts));
+        return project.getRootScriptInfos().every(f => {
+            return f.scriptKind === ScriptKind.JS || f.scriptKind == ScriptKind.JSX || fileExtensionIs(f.fileName, ".d.ts");
+        });
     }
 
     export interface ProjectFilesWithTSDiagnostics extends protocol.ProjectFiles {