diff --git a/src/vs/workbench/api/browser/mainThreadDialogs.ts b/src/vs/workbench/api/browser/mainThreadDialogs.ts
index b4e38d566987be448b9c6f17cbce638bb3673610..94ab09b7eba1babe39263adc9d85375a220ca575 100644
--- a/src/vs/workbench/api/browser/mainThreadDialogs.ts
+++ b/src/vs/workbench/api/browser/mainThreadDialogs.ts
@@ -33,11 +33,11 @@ export class MainThreadDialogs implements MainThreadDiaglogsShape {
 
 	private static _convertOpenOptions(options: MainThreadDialogOpenOptions): IOpenDialogOptions {
 		const result: IOpenDialogOptions = {
-			openLabel: options.openLabel,
+			openLabel: options.openLabel || undefined,
 			canSelectFiles: options.canSelectFiles || (!options.canSelectFiles && !options.canSelectFolders),
 			canSelectFolders: options.canSelectFolders,
 			canSelectMany: options.canSelectMany,
-			defaultUri: URI.revive(options.defaultUri)
+			defaultUri: options.defaultUri ? URI.revive(options.defaultUri) : undefined
 		};
 		if (options.filters) {
 			result.filters = [];
@@ -48,8 +48,8 @@ export class MainThreadDialogs implements MainThreadDiaglogsShape {
 
 	private static _convertSaveOptions(options: MainThreadDialogSaveOptions): ISaveDialogOptions {
 		const result: ISaveDialogOptions = {
-			defaultUri: URI.revive(options.defaultUri),
-			saveLabel: options.saveLabel
+			defaultUri: options.defaultUri ? URI.revive(options.defaultUri) : undefined,
+			saveLabel: options.saveLabel || undefined
 		};
 		if (options.filters) {
 			result.filters = [];