diff --git a/Jakefile.js b/Jakefile.js
index ea81881e7d9c2..c6b1cde9d4e2b 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -23,6 +23,10 @@ else if (process.env.PATH !== undefined) {
 const host = process.env.TYPESCRIPT_HOST || process.env.host || "node";
 
 const defaultTestTimeout = 40000;
+const useBuilt =
+    process.env.USE_BUILT === "true" ? true :
+    process.env.LKG === "true" ? false :
+    false;
 
 let useDebugMode = true;
 
@@ -296,7 +300,7 @@ task(TaskNames.buildFoldEnd, [], function () {
 
 desc("Compiles tslint rules to js");
 task(TaskNames.buildRules, [], function () {
-    tsbuild(ConfigFileFor.lint, false, () => complete());
+    tsbuild(ConfigFileFor.lint, !useBuilt, () => complete());
 }, { async: true });
 
 desc("Cleans the compiler output, declare files, and tests");
@@ -368,7 +372,7 @@ file(ConfigFileFor.tsserverLibrary, [], function () {
 // tsserverlibrary.js
 // tsserverlibrary.d.ts
 file(Paths.tsserverLibraryFile, [TaskNames.coreBuild, ConfigFileFor.tsserverLibrary], function() {
-    tsbuild(ConfigFileFor.tsserverLibrary, false, () => {
+    tsbuild(ConfigFileFor.tsserverLibrary, !useBuilt, () => {
         if (needsUpdate([Paths.tsserverLibraryOutFile, Paths.tsserverLibraryDefinitionOutFile], [Paths.tsserverLibraryFile, Paths.tsserverLibraryDefinitionFile])) {
             const copyright = readFileSync(Paths.copyright);
 
@@ -427,7 +431,7 @@ file(ConfigFileFor.typescriptServices, [], function () {
 // typescriptServices.js
 // typescriptServices.d.ts
 file(Paths.servicesFile, [TaskNames.coreBuild, ConfigFileFor.typescriptServices], function() {
-    tsbuild(ConfigFileFor.typescriptServices, false, () => {
+    tsbuild(ConfigFileFor.typescriptServices, !useBuilt, () => {
         if (needsUpdate([Paths.servicesOutFile, Paths.servicesDefinitionOutFile], [Paths.servicesFile, Paths.servicesDefinitionFile])) {
             const copyright = readFileSync(Paths.copyright);
 
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index ee13a377f5e5e..8f2f0c8cbbd24 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -8346,7 +8346,7 @@ declare namespace ts.server {
         excludedFiles: ReadonlyArray<NormalizedPath>;
         private typeAcquisition;
         updateGraph(): boolean;
-        getExcludedFiles(): readonly NormalizedPath[];
+        getExcludedFiles(): ReadonlyArray<NormalizedPath>;
         getTypeAcquisition(): TypeAcquisition;
         setTypeAcquisition(newTypeAcquisition: TypeAcquisition): void;
     }