diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 1c8593a9e12..545776ec084 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -385,9 +385,9 @@ namespace FourSlash {
         }
 
         // Opens a file given its 0-based index or fileName
-        public openFile(index: number): void;
-        public openFile(name: string): void;
-        public openFile(indexOrName: any) {
+        public openFile(index: number, content?: string): void;
+        public openFile(name: string, content?: string): void;
+        public openFile(indexOrName: any, content?: string) {
             const fileToOpen: FourSlashFile = this.findFile(indexOrName);
             fileToOpen.fileName = ts.normalizeSlashes(fileToOpen.fileName);
             this.activeFile = fileToOpen;
@@ -395,7 +395,7 @@ namespace FourSlash {
             this.scenarioActions.push(`<OpenFile FileName="" SrcFileId="${fileName}" FileId="${fileName}" />`);
 
             // Let the host know that this file is now open
-            this.languageServiceAdapterHost.openFile(fileToOpen.fileName);
+            this.languageServiceAdapterHost.openFile(fileToOpen.fileName, content);
         }
 
         public verifyErrorExistsBetweenMarkers(startMarkerName: string, endMarkerName: string, negative: boolean) {
diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index faf0ad28eb5..0c267c38f14 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -153,7 +153,7 @@ namespace Harness.LanguageService {
             throw new Error("No script with name '" + fileName + "'");
         }
 
-        public openFile(fileName: string): void {
+        public openFile(fileName: string, content?: string): void {
         }
 
         /**
@@ -493,9 +493,9 @@ namespace Harness.LanguageService {
             this.client = client;
         }
 
-        openFile(fileName: string): void {
-            super.openFile(fileName);
-            this.client.openFile(fileName);
+        openFile(fileName: string, content?: string): void {
+            super.openFile(fileName, content);
+            this.client.openFile(fileName, content);
         }
 
         editScript(fileName: string, start: number, end: number, newText: string) {
diff --git a/src/server/client.ts b/src/server/client.ts
index ae234750d88..08939b2b44a 100644
--- a/src/server/client.ts
+++ b/src/server/client.ts
@@ -120,8 +120,8 @@ namespace ts.server {
             return response;
         }
 
-        openFile(fileName: string): void {
-            var args: protocol.FileRequestArgs = { file: fileName };
+        openFile(fileName: string, content?: string): void {
+            var args: protocol.OpenRequestArgs = { file: fileName, fileContent: content };
             this.processRequest(CommandNames.Open, args);
         }
 
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 889c96b6c4e..795bd7db732 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -1031,6 +1031,9 @@ namespace ts.server {
                 }
             }
             if (info) {
+                if (fileContent) {
+                    info.svc.reload(fileContent);
+                }
                 if (openedByClient) {
                     info.isOpen = true;
                 }
diff --git a/src/server/protocol.d.ts b/src/server/protocol.d.ts
index 6354a3a37ae..101c8207c9d 100644
--- a/src/server/protocol.d.ts
+++ b/src/server/protocol.d.ts
@@ -513,6 +513,10 @@ declare namespace ts.server.protocol {
       *  Information found in an "open" request.
       */
     export interface OpenRequestArgs extends FileRequestArgs {
+        /**
+         * Used when a version of the file content is known to be more up to date than the one on disk. 
+         * Then the known content will be used upon opening instead of the disk copy   
+         */ 
         fileContent?: string;
     }
 
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index 41e8d9005f7..f6451e1f1c4 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -169,10 +169,10 @@ module FourSlashInterface {
         // Opens a file, given either its index as it
         // appears in the test source, or its filename
         // as specified in the test metadata
-        public file(index: number);
-        public file(name: string);
-        public file(indexOrName: any) {
-            FourSlash.currentTestState.openFile(indexOrName);
+        public file(index: number, content?: string);
+        public file(name: string, content?: string);
+        public file(indexOrName: any, content?: string) {
+            FourSlash.currentTestState.openFile(indexOrName, content);
         }
     }
 
diff --git a/tests/cases/fourslash/server/openFile.ts b/tests/cases/fourslash/server/openFile.ts
new file mode 100644
index 00000000000..41d2bbe8e53
--- /dev/null
+++ b/tests/cases/fourslash/server/openFile.ts
@@ -0,0 +1,17 @@
+/// <reference path="../fourslash.ts"/>
+
+// @Filename: test1.ts
+////t.
+
+// @Filename: test.ts
+////var t = '10';
+
+// @Filename: tsconfig.json
+////{ "files": ["test.ts", "test1.ts"] }
+
+var overridingContent = "var t = 10; t.";
+debugger;
+goTo.file("test.ts", overridingContent);
+goTo.file("test1.ts");
+goTo.eof();
+verify.completionListContains("toExponential");