diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index ea64b766b66..7bc2d682391 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -47,27 +47,26 @@ declare module 'vscode' {
 		getChildren(element?: T): ProviderResult<T[]>;
 	}
 
-	export interface TreeItem {
+	export class TreeItem {
 		/**
 		 * A human-readable string describing this item
 		 */
-		readonly label: string;
+		label: string;
 
 		/**
 		 * The icon path for the tree item
 		 */
-		readonly iconPath?: string | Uri | { light: string | Uri; dark: string | Uri };
+		iconPath?: string | Uri | { light: string | Uri; dark: string | Uri };
 
 		/**
-		 * The [command](#Command) which should be run when the tree item
-		 * is selected. This command is called with the model representing this item as first argument.
+		 * The [command](#Command) which should be run when the tree item is selected.
 		 */
-		readonly command?: Command;
+		command?: Command;
 
 		/**
 		 * [TreeItemCollapsibleState](#TreeItemCollapsibleState) of the tree item.
 		 */
-		readonly collapsibleState?: TreeItemCollapsibleState;
+		collapsibleState?: TreeItemCollapsibleState;
 
 		/**
 		 * Context value of the tree item. This can be used to contribute item specific actions in the tree.
@@ -87,7 +86,13 @@ declare module 'vscode' {
 		 * ```
 		 * This will show action `extension.deleteFolder` only for items with `contextValue` is `folder`.
 		 */
-		readonly contextValue?: string;
+		contextValue?: string;
+
+		/**
+		 * @param label A human-readable string describing this item
+		 * @param collapsibleState [TreeItemCollapsibleState](#TreeItemCollapsibleState) of the tree item. Default is [TreeItemCollapsibleState.None](#TreeItemCollapsibleState.None)
+		 */
+		constructor(label: string, collapsibleState?: TreeItemCollapsibleState);
 	}
 
 	/**
diff --git a/src/vs/workbench/api/node/extHost.api.impl.ts b/src/vs/workbench/api/node/extHost.api.impl.ts
index 0d14189f2a5..a859a1369fe 100644
--- a/src/vs/workbench/api/node/extHost.api.impl.ts
+++ b/src/vs/workbench/api/node/extHost.api.impl.ts
@@ -535,6 +535,7 @@ export function createApiFactory(
 			WorkspaceEdit: extHostTypes.WorkspaceEdit,
 			ProgressLocation: extHostTypes.ProgressLocation,
 			TreeItemCollapsibleState: extHostTypes.TreeItemCollapsibleState,
+			TreeItem: extHostTypes.TreeItem,
 			ThemeColor: extHostTypes.ThemeColor,
 			// functions
 			TaskRevealKind: extHostTypes.TaskRevealKind,
diff --git a/src/vs/workbench/api/node/extHostTypes.ts b/src/vs/workbench/api/node/extHostTypes.ts
index ef7f35e2a7e..e2967887266 100644
--- a/src/vs/workbench/api/node/extHostTypes.ts
+++ b/src/vs/workbench/api/node/extHostTypes.ts
@@ -1297,6 +1297,17 @@ export enum ProgressLocation {
 	Window = 10,
 }
 
+export class TreeItem {
+
+	iconPath?: string | Uri | { light: string | Uri; dark: string | Uri };
+	command?: vscode.Command;
+	contextValue?: string;
+
+	constructor(public label: string, public collapsibleState: vscode.TreeItemCollapsibleState = TreeItemCollapsibleState.None) {
+	}
+
+}
+
 export enum TreeItemCollapsibleState {
 	None = 0,
 	Collapsed = 1,