diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 272f4c1c1dd..5d73e04c8cb 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -2476,6 +2476,17 @@ module FourSlash {
             }
         }
 
+        // @Filename is the only directive that can be used in a test that contains tsconfig.json file.
+        if (containTSConfigJson(files)) {
+            let directive = getNonFileNameOptionInFileList(files);
+            if (!directive) {
+                directive = getNonFileNameOptionInObject(globalOptions);
+            }
+            if (directive) {
+                throw Error("It is not allowed to use tsconfig.json along with directive '" + directive + "'");
+            }
+        }
+
         return {
             markerPositions,
             markers,
@@ -2485,6 +2496,23 @@ module FourSlash {
         };
     }
 
+    function containTSConfigJson(files: FourSlashFile[]): boolean {
+        return ts.forEach(files, f => f.fileOptions['Filename'] === 'tsconfig.json');
+    }
+
+    function getNonFileNameOptionInFileList(files: FourSlashFile[]): string {
+        return ts.forEach(files, f => getNonFileNameOptionInObject(f.fileOptions));
+    }
+
+    function getNonFileNameOptionInObject(optionObject: { [s: string]: string }): string {
+        for (let option in optionObject) {
+            if (option !== metadataOptionNames.fileName) {
+                return option;
+            }
+        }
+        return undefined;
+    }
+
     const enum State {
         none,
         inSlashStarMarker,
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 91d400ff263..64ec600783a 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -803,9 +803,6 @@ namespace ts.server {
             } else {
                 this.log("no config file");
             }
-            if (configFileName) {
-                configFileName = getAbsolutePath(configFileName, searchPath);
-            }
             if (configFileName && (!this.configProjectIsActive(configFileName))) {
                 var configResult = this.openConfigFile(configFileName, fileName);
                 if (!configResult.success) {
@@ -910,7 +907,8 @@ namespace ts.server {
             configFilename = ts.normalizePath(configFilename);
             // file references will be relative to dirPath (or absolute)
             var dirPath = ts.getDirectoryPath(configFilename);
-            var rawConfig: { config?: ProjectOptions; error?: Diagnostic; } = ts.readConfigFile(configFilename);
+            var contents = this.host.readFile(configFilename)
+            var rawConfig: { config?: ProjectOptions; error?: Diagnostic; } = ts.parseConfigFileText(configFilename, contents);
             if (rawConfig.error) {
                 return rawConfig.error;
             }
diff --git a/tests/cases/fourslash/server/projectInfo.ts b/tests/cases/fourslash/server/projectInfo01.ts
similarity index 100%
rename from tests/cases/fourslash/server/projectInfo.ts
rename to tests/cases/fourslash/server/projectInfo01.ts
diff --git a/tests/cases/fourslash/server/projectInfo02.ts b/tests/cases/fourslash/server/projectInfo02.ts
new file mode 100644
index 00000000000..eb86c721ac7
--- /dev/null
+++ b/tests/cases/fourslash/server/projectInfo02.ts
@@ -0,0 +1,13 @@
+/// <reference path="../fourslash.ts"/>
+
+// @Filename: a.ts
+////export var test = "test String"
+
+// @Filename: b.ts
+////export var test2 = "test String"
+
+// @Filename: tsconfig.json
+////{ "files": ["a.ts", "b.ts"] }
+
+goTo.file("a.ts")
+verify.ProjectInfo(["lib.d.ts", "a.ts", "b.ts"])