diff --git a/types/vis/index.d.ts b/types/vis/index.d.ts
index 1a967d65c6..b55adc6ac8 100644
--- a/types/vis/index.d.ts
+++ b/types/vis/index.d.ts
@@ -1715,19 +1715,19 @@ export interface Locales {
 }
 
 export interface LocaleMessages {
-    edit?: string;
-    del?: string;
-    back?: string;
-    addNode?: string;
-    addEdge?: string;
-    editNode?: string;
-    editEdge?: string;
-    addDescription?: string;
-    edgeDescription?: string;
-    editEdgeDescription?: string;
-    createEdgeError?: string;
-    deleteClusterError?: string;
-    editClusterError?: string;
+    edit: string;
+    del: string;
+    back: string;
+    addNode: string;
+    addEdge: string;
+    editNode: string;
+    editEdge: string;
+    addDescription: string;
+    edgeDescription: string;
+    editEdgeDescription: string;
+    createEdgeError: string;
+    deleteClusterError: string;
+    editClusterError: string;
 }
 
 export interface Options {
diff --git a/types/vis/vis-tests.ts b/types/vis/vis-tests.ts
index a4e9d1d6f8..263baffc79 100644
--- a/types/vis/vis-tests.ts
+++ b/types/vis/vis-tests.ts
@@ -194,7 +194,7 @@ network.setOptions(options2);
 //
 // Test code sample from http://visjs.org/docs/network/#locales
 //
-var locales = {
+const locales = {
   en: {
     edit: 'Edit',
     del: 'Delete selected',
@@ -210,10 +210,10 @@ var locales = {
     deleteClusterError: 'Clusters cannot be deleted.',
     editClusterError: 'Clusters cannot be edited.'
   }
-}
+};
 options = {
   locale: 'en',
-  locales: locales,
-}
+  locales,
+};
 
 network.setOptions(options);