diff --git a/extensions/configuration-editing/src/extension.ts b/extensions/configuration-editing/src/extension.ts
index 644e9bb1192..966073e23f8 100644
--- a/extensions/configuration-editing/src/extension.ts
+++ b/extensions/configuration-editing/src/extension.ts
@@ -7,6 +7,7 @@ import { getLocation, parse, visit } from 'jsonc-parser';
 import * as vscode from 'vscode';
 import * as nls from 'vscode-nls';
 import { SettingsDocument } from './settingsDocumentHelper';
+import { provideInstalledExtensionProposals } from './extensionsProposals';
 const localize = nls.loadMessageBundle();
 
 export function activate(context: vscode.ExtensionContext): void {
@@ -80,7 +81,7 @@ function registerExtensionsCompletionsInExtensionsDocument(): vscode.Disposable
 			const range = document.getWordRangeAtPosition(position) || new vscode.Range(position, position);
 			if (location.path[0] === 'recommendations') {
 				const extensionsContent = <IExtensionsContent>parse(document.getText());
-				return provideInstalledExtensionProposals(extensionsContent, range);
+				return provideInstalledExtensionProposals(extensionsContent && extensionsContent.recommendations || [], range, false);
 			}
 			return [];
 		}
@@ -94,41 +95,13 @@ function registerExtensionsCompletionsInWorkspaceConfigurationDocument(): vscode
 			const range = document.getWordRangeAtPosition(position) || new vscode.Range(position, position);
 			if (location.path[0] === 'extensions' && location.path[1] === 'recommendations') {
 				const extensionsContent = <IExtensionsContent>parse(document.getText())['extensions'];
-				return provideInstalledExtensionProposals(extensionsContent, range);
+				return provideInstalledExtensionProposals(extensionsContent && extensionsContent.recommendations || [], range, false);
 			}
 			return [];
 		}
 	});
 }
 
-function provideInstalledExtensionProposals(extensionsContent: IExtensionsContent, range: vscode.Range): vscode.ProviderResult<vscode.CompletionItem[] | vscode.CompletionList> {
-	const alreadyEnteredExtensions = extensionsContent && extensionsContent.recommendations || [];
-	if (Array.isArray(alreadyEnteredExtensions)) {
-		const knownExtensionProposals = vscode.extensions.all.filter(e =>
-			!(e.id.startsWith('vscode.')
-				|| e.id === 'Microsoft.vscode-markdown'
-				|| alreadyEnteredExtensions.indexOf(e.id) > -1));
-		if (knownExtensionProposals.length) {
-			return knownExtensionProposals.map(e => {
-				const item = new vscode.CompletionItem(e.id);
-				const insertText = `"${e.id}"`;
-				item.kind = vscode.CompletionItemKind.Value;
-				item.insertText = insertText;
-				item.range = range;
-				item.filterText = insertText;
-				return item;
-			});
-		} else {
-			const example = new vscode.CompletionItem(localize('exampleExtension', "Example"));
-			example.insertText = '"vscode.csharp"';
-			example.kind = vscode.CompletionItemKind.Value;
-			example.range = range;
-			return [example];
-		}
-	}
-	return undefined;
-}
-
 vscode.languages.registerDocumentSymbolProvider({ pattern: '**/launch.json', language: 'jsonc' }, {
 	provideDocumentSymbols(document: vscode.TextDocument, _token: vscode.CancellationToken): vscode.ProviderResult<vscode.SymbolInformation[]> {
 		const result: vscode.SymbolInformation[] = [];
diff --git a/extensions/configuration-editing/src/extensionsProposals.ts b/extensions/configuration-editing/src/extensionsProposals.ts
new file mode 100644
index 00000000000..60533ae2975
--- /dev/null
+++ b/extensions/configuration-editing/src/extensionsProposals.ts
@@ -0,0 +1,35 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+import * as nls from 'vscode-nls';
+const localize = nls.loadMessageBundle();
+
+
+export function provideInstalledExtensionProposals(existing: string[], range: vscode.Range, includeBuiltinExtensions: boolean): vscode.ProviderResult<vscode.CompletionItem[] | vscode.CompletionList> {
+	if (Array.isArray(existing)) {
+		const extensions = includeBuiltinExtensions ? vscode.extensions.all : vscode.extensions.all.filter(e => !(e.id.startsWith('vscode.') || e.id === 'Microsoft.vscode-markdown'));
+		const knownExtensionProposals = extensions.filter(e => existing.indexOf(e.id) === -1);
+		if (knownExtensionProposals.length) {
+			return knownExtensionProposals.map(e => {
+				const item = new vscode.CompletionItem(e.id);
+				const insertText = `"${e.id}"`;
+				item.kind = vscode.CompletionItemKind.Value;
+				item.insertText = insertText;
+				item.range = range;
+				item.filterText = insertText;
+				return item;
+			});
+		} else {
+			const example = new vscode.CompletionItem(localize('exampleExtension', "Example"));
+			example.insertText = '"vscode.csharp"';
+			example.kind = vscode.CompletionItemKind.Value;
+			example.range = range;
+			return [example];
+		}
+	}
+	return undefined;
+}
+
diff --git a/extensions/configuration-editing/src/settingsDocumentHelper.ts b/extensions/configuration-editing/src/settingsDocumentHelper.ts
index 3fd25056379..4a7f80c2a2a 100644
--- a/extensions/configuration-editing/src/settingsDocumentHelper.ts
+++ b/extensions/configuration-editing/src/settingsDocumentHelper.ts
@@ -4,8 +4,9 @@
  *--------------------------------------------------------------------------------------------*/
 
 import * as vscode from 'vscode';
-import { getLocation, Location } from 'jsonc-parser';
+import { getLocation, Location, parse } from 'jsonc-parser';
 import * as nls from 'vscode-nls';
+import { provideInstalledExtensionProposals } from './extensionsProposals';
 
 const localize = nls.loadMessageBundle();
 
@@ -13,7 +14,7 @@ export class SettingsDocument {
 
 	constructor(private document: vscode.TextDocument) { }
 
-	public provideCompletionItems(position: vscode.Position, _token: vscode.CancellationToken): vscode.ProviderResult<vscode.CompletionItem[]> {
+	public provideCompletionItems(position: vscode.Position, _token: vscode.CancellationToken): vscode.ProviderResult<vscode.CompletionItem[] | vscode.CompletionList> {
 		const location = getLocation(this.document.getText(), this.document.offsetAt(position));
 		const range = this.document.getWordRangeAtPosition(position) || new vscode.Range(position, position);
 
@@ -41,6 +42,15 @@ export class SettingsDocument {
 			});
 		}
 
+		// sync.ignoredExtensions
+		if (location.path[0] === 'sync.ignoredExtensions') {
+			let ignoredExtensions = [];
+			try {
+				ignoredExtensions = parse(this.document.getText())['sync.ignoredExtensions'];
+			} catch (e) {/* ignore error */ }
+			return provideInstalledExtensionProposals(ignoredExtensions, range, true);
+		}
+
 		return this.provideLanguageOverridesCompletionItems(location, position);
 	}