diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 6001760c4a8..de27376b17d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -49,7 +49,7 @@ namespace ts {
 
         const compilerOptions = host.getCompilerOptions();
         const languageVersion = compilerOptions.target || ScriptTarget.ES3;
-        const modulekind = typeof compilerOptions.module === "number" ? compilerOptions.module : languageVersion === ScriptTarget.ES6 ? ModuleKind.ES6 : ModuleKind.CommonJS;
+        const modulekind = getEmitModuleKind(compilerOptions);
         const allowSyntheticDefaultImports = typeof compilerOptions.allowSyntheticDefaultImports !== "undefined" ? compilerOptions.allowSyntheticDefaultImports : modulekind === ModuleKind.System;
 
         const emitResolver = createResolver();
diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index 82c6b852e23..d21a4b00a03 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -580,7 +580,6 @@ namespace ts {
         const options: CompilerOptions = {};
         const errors: Diagnostic[] = [];
 
-        options.module = ModuleKind.CommonJS;
         if (configFileName && getBaseFileName(configFileName) === "jsconfig.json") {
             options.allowJs = true;
         }
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 3c75f31add2..bd811b9bea3 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -1290,7 +1290,7 @@ namespace ts {
 
             const firstExternalModuleSourceFile = forEach(files, f => isExternalModule(f) ? f : undefined);
             if (options.isolatedModules) {
-                if (!options.module && languageVersion < ScriptTarget.ES6) {
+                if (options.module === ModuleKind.None && languageVersion < ScriptTarget.ES6) {
                     programDiagnostics.add(createCompilerDiagnostic(Diagnostics.Option_isolatedModules_can_only_be_used_when_either_option_module_is_provided_or_option_target_is_ES2015_or_higher));
                 }
 
@@ -1300,7 +1300,7 @@ namespace ts {
                     programDiagnostics.add(createFileDiagnostic(firstNonExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_compile_namespaces_when_the_isolatedModules_flag_is_provided));
                 }
             }
-            else if (firstExternalModuleSourceFile && languageVersion < ScriptTarget.ES6 && !options.module) {
+            else if (firstExternalModuleSourceFile && languageVersion < ScriptTarget.ES6 && options.module === ModuleKind.None) {
                 // We cannot use createDiagnosticFromNode because nodes do not have parents yet
                 const span = getErrorSpanForNode(firstExternalModuleSourceFile, firstExternalModuleSourceFile.externalModuleIndicator);
                 programDiagnostics.add(createFileDiagnostic(firstExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_compile_modules_unless_the_module_flag_is_provided_Consider_setting_the_module_compiler_option_in_a_tsconfig_json_file));
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 7fd81973172..3536c6f113d 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -974,7 +974,6 @@ namespace Harness {
 
             const options: ts.CompilerOptions & HarnessOptions = compilerOptions ? ts.clone(compilerOptions) : { noResolve: false };
             options.target = options.target || ts.ScriptTarget.ES3;
-            options.module = options.module || ts.ModuleKind.None;
             options.newLine = options.newLine || ts.NewLineKind.CarriageReturnLineFeed;
             options.noErrorTruncation = true;
             options.skipDefaultLibCheck = true;
diff --git a/src/services/services.ts b/src/services/services.ts
index 7a767011176..0fb7f329dfe 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1712,7 +1712,6 @@ namespace ts {
         // Always default to "ScriptTarget.ES5" for the language service
         return {
             target: ScriptTarget.ES5,
-            module: ModuleKind.CommonJS,
             jsx: JsxEmit.Preserve
         };
     }