diff --git a/src/vs/workbench/api/browser/mainThreadWindow.ts b/src/vs/workbench/api/browser/mainThreadWindow.ts
index bbce19a3388..e03411f1823 100644
--- a/src/vs/workbench/api/browser/mainThreadWindow.ts
+++ b/src/vs/workbench/api/browser/mainThreadWindow.ts
@@ -10,6 +10,8 @@ import { IOpenerService } from 'vs/platform/opener/common/opener';
 import { extHostNamedCustomer } from 'vs/workbench/api/common/extHostCustomers';
 import { ExtHostContext, ExtHostWindowShape, IExtHostContext, IOpenUriOptions, MainContext, MainThreadWindowShape } from '../common/extHost.protocol';
 import { IHostService } from 'vs/workbench/services/host/browser/host';
+import { Schemas } from 'vs/base/common/network';
+import { isFalsyOrWhitespace } from 'vs/base/common/strings';
 
 @extHostNamedCustomer(MainContext.MainThreadWindow)
 export class MainThreadWindow implements MainThreadWindowShape {
@@ -42,9 +44,25 @@ export class MainThreadWindow implements MainThreadWindowShape {
 		return Promise.resolve(this.hostService.hasFocus);
 	}
 
-	async $openUri(uriComponents: UriComponents, options: IOpenUriOptions): Promise<boolean> {
-		const uri = URI.from(uriComponents);
-		return this.openerService.open(uri, { openExternal: true, allowTunneling: options.allowTunneling });
+	async $openUri(stringOrComp: UriComponents | string, options: IOpenUriOptions): Promise<boolean> {
+
+		const uri = typeof stringOrComp === 'string'
+			? URI.parse(stringOrComp)
+			: URI.revive(stringOrComp);
+
+		// validate
+		if (isFalsyOrWhitespace(uri.scheme)) {
+			return Promise.reject('Invalid scheme - cannot be empty');
+		} else if (uri.scheme === Schemas.command) {
+			return Promise.reject(`Invalid scheme '${uri.scheme}'`);
+		}
+
+		// open AS-IS, keep string alive
+		if (typeof stringOrComp === 'string') {
+			return this.openerService.open(stringOrComp, { openExternal: true, allowTunneling: options.allowTunneling });
+		} else {
+			return this.openerService.open(uri, { openExternal: true, allowTunneling: options.allowTunneling });
+		}
 	}
 
 	async $asExternalUri(uriComponents: UriComponents, options: IOpenUriOptions): Promise<UriComponents> {
diff --git a/src/vs/workbench/api/common/extHost.protocol.ts b/src/vs/workbench/api/common/extHost.protocol.ts
index 9bc433a1727..3ce80496914 100644
--- a/src/vs/workbench/api/common/extHost.protocol.ts
+++ b/src/vs/workbench/api/common/extHost.protocol.ts
@@ -759,7 +759,7 @@ export interface IOpenUriOptions {
 
 export interface MainThreadWindowShape extends IDisposable {
 	$getWindowVisibility(): Promise<boolean>;
-	$openUri(uri: UriComponents, options: IOpenUriOptions): Promise<boolean>;
+	$openUri(uri: UriComponents | string, options: IOpenUriOptions): Promise<boolean>;
 	$asExternalUri(uri: UriComponents, options: IOpenUriOptions): Promise<UriComponents>;
 }
 
diff --git a/src/vs/workbench/api/common/extHostRequireInterceptor.ts b/src/vs/workbench/api/common/extHostRequireInterceptor.ts
index b6f94048fbd..6f8fc58d0b8 100644
--- a/src/vs/workbench/api/common/extHostRequireInterceptor.ts
+++ b/src/vs/workbench/api/common/extHostRequireInterceptor.ts
@@ -19,6 +19,8 @@ import { IInstantiationService } from 'vs/platform/instantiation/common/instanti
 import { IExtHostExtensionService } from 'vs/workbench/api/common/extHostExtensionService';
 import { platform } from 'vs/base/common/process';
 import { ILogService } from 'vs/platform/log/common/log';
+import { matchesScheme } from 'vs/platform/opener/common/opener';
+import { Schemas } from 'vs/base/common/network';
 
 
 interface LoadFunction {
@@ -239,15 +241,15 @@ class OpenNodeModuleFactory implements INodeModuleFactory {
 		const mainThreadWindow = rpcService.getProxy(MainContext.MainThreadWindow);
 
 		this._impl = (target, options) => {
-			const uri: URI = URI.parse(target);
 			// If we have options use the original method.
 			if (options) {
 				return this.callOriginal(target, options);
 			}
-			if (uri.scheme === 'http' || uri.scheme === 'https') {
-				return mainThreadWindow.$openUri(uri, { allowTunneling: true });
-			} else if (uri.scheme === 'mailto' || uri.scheme === this._appUriScheme) {
-				return mainThreadWindow.$openUri(uri, {});
+			if (matchesScheme(target, Schemas.http) || matchesScheme(target, Schemas.https)) {
+				return mainThreadWindow.$openUri(target, { allowTunneling: true });
+
+			} else if (matchesScheme(target, Schemas.mailto) || matchesScheme(target, this._appUriScheme)) {
+				return mainThreadWindow.$openUri(target, {});
 			}
 			return this.callOriginal(target, options);
 		};
diff --git a/src/vs/workbench/api/common/extHostWindow.ts b/src/vs/workbench/api/common/extHostWindow.ts
index 8ce82ac8b2d..d86a9203f3c 100644
--- a/src/vs/workbench/api/common/extHostWindow.ts
+++ b/src/vs/workbench/api/common/extHostWindow.ts
@@ -39,18 +39,6 @@ export class ExtHostWindow implements ExtHostWindowShape {
 	}
 
 	openUri(stringOrUri: string | URI, options: IOpenUriOptions): Promise<boolean> {
-		if (typeof stringOrUri === 'string') {
-			try {
-				stringOrUri = URI.parse(stringOrUri);
-			} catch (e) {
-				return Promise.reject(`Invalid uri - '${stringOrUri}'`);
-			}
-		}
-		if (isFalsyOrWhitespace(stringOrUri.scheme)) {
-			return Promise.reject('Invalid scheme - cannot be empty');
-		} else if (stringOrUri.scheme === Schemas.command) {
-			return Promise.reject(`Invalid scheme '${stringOrUri.scheme}'`);
-		}
 		return this._proxy.$openUri(stringOrUri, options);
 	}