diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index 2f10a8103c4..59ebf01d47f 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -590,9 +590,9 @@ namespace ts {
       */
     export function parseJsonConfigFileContent(json: any, host: ParseConfigHost, basePath: string, existingOptions: CompilerOptions = {}, configFileName?: string): ParsedCommandLine {
         const errors: Diagnostic[] = [];
-        const compilerOptions: CompilerOptions = convertCompilerOptionsFromJson(optionDeclarations, json["compilerOptions"], basePath, errors, configFileName);
+        const compilerOptions: CompilerOptions = convertCompilerOptionsFromJsonWorker(json["compilerOptions"], basePath, errors, configFileName);
         const options = extend(existingOptions, compilerOptions);
-        const typingOptions: TypingOptions = convertTypingOptionsFromJson(typingOptionDeclarations, json["typingOptions"], basePath, errors, configFileName);
+        const typingOptions: TypingOptions = convertTypingOptionsFromJsonWorker(json["typingOptions"], basePath, errors, configFileName);
 
         const fileNames = getFileNames(errors);
 
@@ -666,28 +666,38 @@ namespace ts {
         }
     }
 
-    /* @internal */
-    export function convertCompilerOptionsFromJson(optionsDeclarations: CommandLineOption[], jsonOptions: any,
+    export function convertCompilerOptionsFromJson(jsonOptions: any, basePath: string, configFileName?: string): { options: CompilerOptions, errors: Diagnostic[] } {
+        const errors: Diagnostic[] = [];
+        const options = convertCompilerOptionsFromJsonWorker(jsonOptions, basePath, errors, configFileName);
+        return { options, errors };
+    }
+
+    export function convertTypingOptionsFromJson(jsonOptions: any, basePath: string, configFileName?: string): { options: CompilerOptions, errors: Diagnostic[] } {
+        const errors: Diagnostic[] = [];
+        const options = convertTypingOptionsFromJsonWorker(jsonOptions, basePath, errors, configFileName);
+        return { options, errors };
+    }
+
+    function convertCompilerOptionsFromJsonWorker(jsonOptions: any,
         basePath: string, errors: Diagnostic[], configFileName?: string): CompilerOptions {
 
         const options: CompilerOptions = getBaseFileName(configFileName) === "jsconfig.json" ? { allowJs: true } : {};
-        convertOptionsFromJson<CompilerOptions>(optionDeclarations, jsonOptions, basePath, options, Diagnostics.Unknown_compiler_option_0, errors);
+        convertOptionsFromJson(optionDeclarations, jsonOptions, basePath, options, Diagnostics.Unknown_compiler_option_0, errors);
         return options;
     }
 
-    /* @internal */
-    export function convertTypingOptionsFromJson(optionsDeclarations: CommandLineOption[], jsonOptions: any,
+    function convertTypingOptionsFromJsonWorker(jsonOptions: any,
         basePath: string, errors: Diagnostic[], configFileName?: string): TypingOptions {
 
         const options: TypingOptions = getBaseFileName(configFileName) === "jsconfig.json"
             ? { enableAutoDiscovery: true, include: [], exclude: [] }
             : { enableAutoDiscovery: false, include: [], exclude: [] };
-        convertOptionsFromJson<TypingOptions>(typingOptionDeclarations, jsonOptions, basePath, options, Diagnostics.Unknown_typing_option_0, errors);
+        convertOptionsFromJson(typingOptionDeclarations, jsonOptions, basePath, options, Diagnostics.Unknown_typing_option_0, errors);
         return options;
     }
 
-    function convertOptionsFromJson<T extends CompilerOptions | TypingOptions>(optionDeclarations: CommandLineOption[], jsonOptions: any, basePath: string,
-        defaultOptions: T, diagnosticMessage: DiagnosticMessage, errors: Diagnostic[]) {
+    function convertOptionsFromJson(optionDeclarations: CommandLineOption[], jsonOptions: any, basePath: string,
+        defaultOptions: CompilerOptions | TypingOptions, diagnosticMessage: DiagnosticMessage, errors: Diagnostic[]) {
 
         if (!jsonOptions) {
             return ;
diff --git a/tests/cases/unittests/convertCompilerOptionsFromJson.ts b/tests/cases/unittests/convertCompilerOptionsFromJson.ts
index 4edc3bdd200..7ac80be7892 100644
--- a/tests/cases/unittests/convertCompilerOptionsFromJson.ts
+++ b/tests/cases/unittests/convertCompilerOptionsFromJson.ts
@@ -4,8 +4,7 @@
 namespace ts {
     describe('convertCompilerOptionsFromJson', () => {
         function assertCompilerOptions(json: any, configFileName: string, expectedResult: { compilerOptions: CompilerOptions, errors: Diagnostic[] }) {
-            const actualErrors: Diagnostic[] = [];
-            const actualCompilerOptions: CompilerOptions = convertCompilerOptionsFromJson(optionDeclarations, json["compilerOptions"], "/apath/", actualErrors, configFileName);
+            const { options: actualCompilerOptions, errors: actualErrors} = convertCompilerOptionsFromJson(json["compilerOptions"], "/apath/", configFileName);
             
             const parsedCompilerOptions = JSON.stringify(actualCompilerOptions);
             const expectedCompilerOptions = JSON.stringify(expectedResult.compilerOptions);
diff --git a/tests/cases/unittests/convertTypingOptionsFromJson.ts b/tests/cases/unittests/convertTypingOptionsFromJson.ts
index 92b450555a9..3cd15a17c61 100644
--- a/tests/cases/unittests/convertTypingOptionsFromJson.ts
+++ b/tests/cases/unittests/convertTypingOptionsFromJson.ts
@@ -4,8 +4,7 @@
 namespace ts {
     describe('convertTypingOptionsFromJson', () => {
         function assertTypingOptions(json: any, configFileName: string, expectedResult: { typingOptions: TypingOptions, errors: Diagnostic[] }) {
-            const actualErrors: Diagnostic[] = [];
-            const actualTypingOptions = convertTypingOptionsFromJson(typingOptionDeclarations, json["typingOptions"], "/apath/", actualErrors, configFileName);
+            const { options: actualTypingOptions, errors: actualErrors } = convertTypingOptionsFromJson(json["typingOptions"], "/apath/", configFileName);
             const parsedTypingOptions = JSON.stringify(actualTypingOptions);
             const expectedTypingOptions = JSON.stringify(expectedResult.typingOptions);
             assert.equal(parsedTypingOptions, expectedTypingOptions);