diff --git a/TODO b/TODO
index 694dab4..edac1bd 100644
--- a/TODO
+++ b/TODO
@@ -1,26 +1,25 @@
 MVP
 ===
 - lint everything
-- delete lint on close file
 
 TODO
 ====
 - lint current file
 - [v] command clear all issues
 
 Long Term Desired Features
 ==========================
 - Fancy UIs for
     - arc patch
     - arc todo
     - arc unit
     - arc browse
     - arc paste (upload and download)
 - list open Differential in repo (for review)
 - get hovercard (content) for any object
 - push notifications from website ?
 - preview Remarkup
 - some magic to help the External Editor Link
 - arc lint: special-case some messages for better visibility (find more range/information.)
 - arc lint: support auto-fix (apply diff)
 - arc lint: `locations` field may be parsed into `relatedInformation`.
diff --git a/src/extension.ts b/src/extension.ts
index 51646ab..976089c 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -1,44 +1,45 @@
 import * as vscode from 'vscode';
 import * as lint from './arc_lint';
 
 export function activate(context: vscode.ExtensionContext) {
-	const collection = vscode.languages.createDiagnosticCollection('arc lint');
+	const diagnostics = vscode.languages.createDiagnosticCollection('arc lint');
 
 	lint.setup();
 
 	function d(disposable: vscode.Disposable) {
 		context.subscriptions.push(disposable);
 	}
+	d(diagnostics);
 
-	d(vscode.commands.registerCommand('arc-vscode.clearLint', () => collection.clear()));
+	d(vscode.commands.registerCommand('arc-vscode.clearLint', () => diagnostics.clear()));
 
 	d(vscode.workspace.onDidSaveTextDocument(onTextDocumentEvent));
 	d(vscode.workspace.onDidOpenTextDocument(onTextDocumentEvent));
 	d(vscode.workspace.onDidChangeConfiguration(onChangeConfig));
 
 	if (vscode.window.activeTextEditor) {
-		lint.lintFile(vscode.window.activeTextEditor.document, collection);
+		lint.lintFile(vscode.window.activeTextEditor.document, diagnostics);
 	}
 
 	d(vscode.window.onDidChangeActiveTextEditor(editor => {
 		if (editor) {
-			lint.lintFile(editor.document, collection);
+			lint.lintFile(editor.document, diagnostics);
 		}
 	}));
 
+	d(vscode.workspace.onDidCloseTextDocument(document => diagnostics.delete(document.uri)));
+
 	function onTextDocumentEvent(document: vscode.TextDocument) {
-		lint.lintFile(document, collection);
+		lint.lintFile(document, diagnostics);
 	}
 
 }
 
-export function deactivate() {
-	// TODO collection.clear();
-}
+export function deactivate() { }
 
 function onChangeConfig(e: vscode.ConfigurationChangeEvent) {
 	if (!e.affectsConfiguration('arc-vscode.lint')) {
 		return;
 	}
 	lint.updateLintSeverityMap();
 }