diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 9d79d435a04..976107e540c 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -566,7 +566,7 @@ namespace ts {
 
     function writeConfigFile(options: CompilerOptions, fileNames: string[]) {
         let currentDirectory = sys.getCurrentDirectory();
-        let file = combinePaths(currentDirectory, "tsconfig.json");
+        let file = normalizePath(combinePaths(currentDirectory, "tsconfig.json"));
         if (sys.fileExists(file)) {
             reportDiagnostic(createCompilerDiagnostic(Diagnostics.A_tsconfig_json_file_is_already_defined_at_Colon_0, file));
         }