diff --git a/src/vs/vscode.d.ts b/src/vs/vscode.d.ts
index 5ce1237ebd6..efe3eb07a9b 100644
--- a/src/vs/vscode.d.ts
+++ b/src/vs/vscode.d.ts
@@ -4471,6 +4471,9 @@ declare module 'vscode' {
 		 *     script: string;
 		 * }
 		 * ```
+		 *
+		 * Note that type identifier starting with a '$' are reserved for internal
+		 * usages and shouldn't be used by extensions.
 		 */
 		readonly type: string;
 
diff --git a/src/vs/workbench/api/electron-browser/mainThreadTask.ts b/src/vs/workbench/api/electron-browser/mainThreadTask.ts
index cd32296c9da..75f08197085 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadTask.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadTask.ts
@@ -285,9 +285,6 @@ namespace TaskDTO {
 				}
 			}
 		}
-		if (!result.execution) {
-			return undefined;
-		}
 		return result;
 	}
 
diff --git a/src/vs/workbench/api/node/extHostTask.ts b/src/vs/workbench/api/node/extHostTask.ts
index 024ad5f56b0..194121f17cc 100644
--- a/src/vs/workbench/api/node/extHostTask.ts
+++ b/src/vs/workbench/api/node/extHostTask.ts
@@ -610,7 +610,7 @@ namespace TaskDTO {
 				scope = value.scope.uri.toJSON();
 			}
 		}
-		if (!execution || !definition || !scope) {
+		if (!definition || !scope) {
 			return undefined;
 		}
 		let group = (value.group as types.TaskGroup) ? (value.group as types.TaskGroup).id : undefined;
@@ -655,7 +655,7 @@ namespace TaskDTO {
 				scope = types.TaskScope.Workspace;
 			}
 		}
-		if (!execution || !definition || !scope) {
+		if (!definition || !scope) {
 			return undefined;
 		}
 		let result = new types.Task(definition, scope, value.name, value.source.label, execution, value.problemMatchers);
diff --git a/src/vs/workbench/parts/tasks/common/taskDefinitionRegistry.ts b/src/vs/workbench/parts/tasks/common/taskDefinitionRegistry.ts
index cc197afc0ce..7a2bab4ba3a 100644
--- a/src/vs/workbench/parts/tasks/common/taskDefinitionRegistry.ts
+++ b/src/vs/workbench/parts/tasks/common/taskDefinitionRegistry.ts
@@ -22,7 +22,7 @@ const taskDefinitionSchema: IJSONSchema = {
 	properties: {
 		type: {
 			type: 'string',
-			description: nls.localize('TaskDefinition.description', 'The actual task type')
+			description: nls.localize('TaskDefinition.description', 'The actual task type. Please note that types starting with a \'$\' are reserved for internal usage.')
 		},
 		required: {
 			type: 'array',
diff --git a/src/vs/workbench/parts/tasks/common/tasks.ts b/src/vs/workbench/parts/tasks/common/tasks.ts
index 8fd3e0fc004..bfdbdad02e7 100644
--- a/src/vs/workbench/parts/tasks/common/tasks.ts
+++ b/src/vs/workbench/parts/tasks/common/tasks.ts
@@ -7,14 +7,12 @@
 import * as Types from 'vs/base/common/types';
 import { IJSONSchemaMap } from 'vs/base/common/jsonSchema';
 import * as Objects from 'vs/base/common/objects';
-import { generateUuid } from 'vs/base/common/uuid';
 import { UriComponents } from 'vs/base/common/uri';
 
 import { IExtensionDescription } from 'vs/workbench/services/extensions/common/extensions';
 import { ProblemMatcher } from 'vs/workbench/parts/tasks/common/problemMatcher';
 import { IWorkspaceFolder } from 'vs/platform/workspace/common/workspace';
 
-
 export enum ShellQuoting {
 	/**
 	 * Default is character escaping.
@@ -445,20 +443,18 @@ export namespace CustomTask {
 		return candidate && candidate.type === 'custom';
 	}
 	export function getDefinition(task: CustomTask): TaskIdentifier {
-		if (task.command === void 0) {
-			return undefined;
-		}
-		if (task.command.runtime === RuntimeType.Shell) {
-			return {
-				_key: generateUuid(),
-				type: 'shell'
-			};
+		let type: string;
+		if (task.command !== void 0) {
+			type = task.command.runtime === RuntimeType.Shell ? 'shell' : 'process';
 		} else {
-			return {
-				_key: generateUuid(),
-				type: 'process'
-			};
+			type = '$composite';
 		}
+		let result: TaskIdentifier = {
+			type,
+			_key: task._id,
+			id: task._id
+		};
+		return result;
 	}
 }
 
@@ -617,7 +613,7 @@ export namespace Task {
 	export function getTaskDefinition(task: Task): TaskIdentifier {
 		if (ContributedTask.is(task)) {
 			return task.defines;
-		} else if (CustomTask.is(task) && task.command !== void 0) {
+		} else if (CustomTask.is(task)) {
 			return CustomTask.getDefinition(task);
 		} else {
 			return undefined;