diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 37bbffee43a..372521d6c14 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -44,7 +44,7 @@ namespace ts {
 
         let compilerOptions = host.getCompilerOptions();
         let languageVersion = compilerOptions.target || ScriptTarget.ES3;
-        var modulekind = compilerOptions.module ? compilerOptions.module : languageVersion === ScriptTarget.ES6 ? ModuleKind.ES6 : ModuleKind.None;
+        let modulekind = compilerOptions.module ? compilerOptions.module : languageVersion === ScriptTarget.ES6 ? ModuleKind.ES6 : ModuleKind.None;
 
         let emitResolver = createResolver();
 
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 1c5b101f5a7..4e6d96961a9 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -64,7 +64,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
 
         let compilerOptions = host.getCompilerOptions();
         let languageVersion = compilerOptions.target || ScriptTarget.ES3;
-        var modulekind = compilerOptions.module ? compilerOptions.module : languageVersion === ScriptTarget.ES6 ? ModuleKind.ES6 : ModuleKind.None;
+        let modulekind = compilerOptions.module ? compilerOptions.module : languageVersion === ScriptTarget.ES6 ? ModuleKind.ES6 : ModuleKind.None;
         let sourceMapDataList: SourceMapData[] = compilerOptions.sourceMap || compilerOptions.inlineSourceMap ? [] : undefined;
         let diagnostics: Diagnostic[] = [];
         let newLine = host.getNewLine();