diff --git a/adapter/package.json b/adapter/package.json
index 94424d0..8a1abd8 100644
--- a/adapter/package.json
+++ b/adapter/package.json
@@ -1,7 +1,7 @@
 {
 	"name": "vscode-debugadapter",
 	"description": "Debug adapter implementation for node",
-	"version": "1.15.0-pre.3",
+	"version": "1.15.0-pre.4",
 	"author": "Microsoft Corporation",
 	"license": "MIT",
 	"repository": {
@@ -14,7 +14,7 @@
 	"main": "./lib/main.js",
 	"typings": "./lib/main",
 	"dependencies": {
-		"vscode-debugprotocol": "^1.15.0-pre.3"
+		"vscode-debugprotocol": "^1.15.0-pre.4"
 	},
 	"devDependencies": {
 		"typescript": "^1.8.10"
diff --git a/debugProtocol.json b/debugProtocol.json
index 71822b8..33b66bb 100644
--- a/debugProtocol.json
+++ b/debugProtocol.json
@@ -259,7 +259,7 @@
 		"OutputEvent": {
 			"allOf": [ { "$ref": "#/definitions/Event" }, {
 				"type": "object",
-				"description": "Event message for 'output' event type.\nThe event indicates that the target has produced output.",
+				"description": "Event message for 'output' event type.\nThe event indicates that the target has produced some output.",
 				"properties": {
 					"event": {
 						"type": "string",
@@ -277,6 +277,10 @@
 								"type": "string",
 								"description": "The output to report."
 							},
+							"variablesReference": {
+								"type": "number",
+								"description": "If an attribute 'variablesReference' exists and its value is > 0, the output contains objects which can be retrieved by passing variablesReference to the VariablesRequest."
+							},
 							"data": {
 								"type": [ "array", "boolean", "integer", "null", "number" , "object", "string" ],
 								"description": "Optional data to report. For the 'telemetry' category the data will be sent to telemetry, for the other categories the data is shown in JSON format."
diff --git a/protocol/README.md b/protocol/README.md
index 2e808bf..b39ac16 100644
--- a/protocol/README.md
+++ b/protocol/README.md
@@ -10,6 +10,7 @@ This npm module contains declarations for the json-based Visual Studio Code debu
 * 1.15.x:
   * Adds a `reverseContinue` request.
   * Adds a `restart` request and a corresponding `supportsRestartRequest` capability.
+  * Adds a `variablesReference` attribute to the `OutputEvent`.
 
 * 1.14.x:
   * Adds optional `type` attribute to the `SetVariableResponse` type.
diff --git a/protocol/package.json b/protocol/package.json
index dc86a01..8f9ab0a 100644
--- a/protocol/package.json
+++ b/protocol/package.json
@@ -1,7 +1,7 @@
 {
 	"name": "vscode-debugprotocol",
 	"description": "Npm module with declarations for the Visual Studio Code debug protocol",
-	"version": "1.15.0-pre.3",
+	"version": "1.15.0-pre.4",
 	"author": "Microsoft Corporation",
 	"license": "MIT",
 	"repository": {
diff --git a/protocol/src/debugProtocol.ts b/protocol/src/debugProtocol.ts
index 33092ae..fb16e1f 100644
--- a/protocol/src/debugProtocol.ts
+++ b/protocol/src/debugProtocol.ts
@@ -138,7 +138,7 @@ export module DebugProtocol {
 	}
 
 	/** Event message for 'output' event type.
-		The event indicates that the target has produced output.
+		The event indicates that the target has produced some output.
 	*/
 	export interface OutputEvent extends Event {
 		// event: 'output';
@@ -147,6 +147,8 @@ export module DebugProtocol {
 			category?: string;
 			/** The output to report. */
 			output: string;
+			/** If an attribute 'variablesReference' exists and its value is > 0, the output contains objects which can be retrieved by passing variablesReference to the VariablesRequest. */
+			variablesReference?: number;
 			/** Optional data to report. For the 'telemetry' category the data will be sent to telemetry, for the other categories the data is shown in JSON format. */
 			data?: any;
 		};