diff --git a/src/vs/workbench/api/browser/viewsContainersExtensionPoint.ts b/src/vs/workbench/api/browser/viewsContainersExtensionPoint.ts
index 5fd69ca019e..6b91f2d6634 100644
--- a/src/vs/workbench/api/browser/viewsContainersExtensionPoint.ts
+++ b/src/vs/workbench/api/browser/viewsContainersExtensionPoint.ts
@@ -114,11 +114,11 @@ class ViewsContainersExtensionHandler implements IWorkbenchContribution {
 
 		for (let descriptor of viewsContainersDescriptors) {
 			if (typeof descriptor.id !== 'string') {
-				collector.error(localize('requireidstring', "property `{0}` is mandatory and must be of type `string`. Allowed only alphanumeric letters, '_', '-'.", 'id'));
+				collector.error(localize('requireidstring', "property `{0}` is mandatory and must be of type `string`. Only alphanumeric characters, '_', and '-' are allowed.", 'id'));
 				return false;
 			}
 			if (!(/^[a-z0-9_-]+$/i.test(descriptor.id))) {
-				collector.error(localize('requireidstring', "property `{0}` is mandatory and must be of type `string`. Allowed only alphanumeric letters, '_', '-'.", 'id'));
+				collector.error(localize('requireidstring', "property `{0}` is mandatory and must be of type `string`. Only alphanumeric characters, '_', and '-' are allowed.", 'id'));
 				return false;
 			}
 			if (typeof descriptor.title !== 'string') {