diff --git a/src/monaco.d.ts b/src/monaco.d.ts
index 417f73bc..d79f3a35 100644
--- a/src/monaco.d.ts
+++ b/src/monaco.d.ts
@@ -8,33 +8,33 @@ declare module monaco.languages.json {
         /**
          * If set, the validator will be enabled and perform syntax validation as well as schema based validation.
          */
-        validate?: boolean;
+        readonly validate?: boolean;
         /**
          * If set, comments are tolerated. If set to false, syntax errors will be emmited for comments.
          */
-        allowComments?: boolean;
+        readonly allowComments?: boolean;
         /**
          * A list of known schemas and/or associations of schemas to file names.
          */
-        schemas?: {
+        readonly schemas?: {
             /**
              * The URI of the schema, which is also the identifier of the schema.
              */
-            uri: string;
+            readonly uri: string;
             /**
              * A list of file names that are associated to the schema. The '*' wildcard can be used. For example '*.schema.json', 'package.json'
              */
-            fileMatch?: string[];
+            readonly fileMatch?: string[];
             /**
              * The schema for the given URI.
              */
-            schema?: any;
+            readonly schema?: any;
         }[];
     }
 
     export interface LanguageServiceDefaults {
-        onDidChange: IEvent<LanguageServiceDefaults>;
-        diagnosticsOptions: DiagnosticsOptions;
+        readonly onDidChange: IEvent<LanguageServiceDefaults>;
+        readonly diagnosticsOptions: DiagnosticsOptions;
         setDiagnosticsOptions(options: DiagnosticsOptions): void;
     }