diff --git a/src/highlight.js b/src/highlight.js
index 8f59f1ae9c..4f98f38ea5 100644
--- a/src/highlight.js
+++ b/src/highlight.js
@@ -20,6 +20,7 @@ const NO_MATCH = Symbol("nomatch");
 
 /**
  * @param {any} hljs - object that is extended (legacy)
+ * @returns {HLJSApi}
  */
 const HLJS = function(hljs) {
   // Convenience variables for build-in objects
diff --git a/types/index.d.ts b/types/index.d.ts
index b9eb0d317a..59fd9d1926 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -210,3 +210,22 @@ interface ModeDetails {
     subLanguage?: string | string[]
     compiled?: boolean
 }
+
+// deprecated API since v10
+// declare module 'highlight.js/lib/highlight.js';
+
+declare module 'highlight.js' {
+    export = hljs;
+}
+
+declare module 'highlight.js/lib/core' {
+    export = hljs;
+}
+
+declare module 'highlight.js/lib/core.js' {
+    export = hljs;
+}
+
+declare module 'highlight.js/lib/languages/*' {
+    export default function(hljs?: HLJSApi): LanguageDetail;
+}