diff --git a/src/vs/workbench/services/extensions/electron-browser/localProcessExtensionHost.ts b/src/vs/workbench/services/extensions/electron-browser/localProcessExtensionHost.ts
index 27289266b5b..8669f21221a 100644
--- a/src/vs/workbench/services/extensions/electron-browser/localProcessExtensionHost.ts
+++ b/src/vs/workbench/services/extensions/electron-browser/localProcessExtensionHost.ts
@@ -212,6 +212,11 @@ export class LocalProcessExtensionHost implements IExtensionHost {
 
 				this._extensionHostProcess = new ExtensionHostProcess(extensionHostCreationResult.id, this._extensionHostStarter);
 
+				let lang = processEnv['LANG'];
+				if (platform.isMacintosh && lang === undefined) {
+					lang = Intl.DateTimeFormat().resolvedOptions().locale;
+				}
+
 				const env = objects.mixin(processEnv, {
 					VSCODE_AMD_ENTRYPOINT: 'vs/workbench/api/node/extensionHostProcess',
 					VSCODE_PIPE_LOGGING: 'true',
@@ -219,7 +224,8 @@ export class LocalProcessExtensionHost implements IExtensionHost {
 					VSCODE_LOG_NATIVE: this._isExtensionDevHost,
 					VSCODE_IPC_HOOK_EXTHOST: pipeName,
 					VSCODE_HANDLES_UNCAUGHT_ERRORS: true,
-					VSCODE_LOG_STACK: !this._isExtensionDevTestFromCli && (this._isExtensionDevHost || !this._environmentService.isBuilt || this._productService.quality !== 'stable' || this._environmentService.verbose)
+					VSCODE_LOG_STACK: !this._isExtensionDevTestFromCli && (this._isExtensionDevHost || !this._environmentService.isBuilt || this._productService.quality !== 'stable' || this._environmentService.verbose),
+					'LANG': lang
 				});
 
 				if (this._environmentService.debugExtensionHost.env) {