diff --git a/natural/natural.d.ts b/natural/natural.d.ts
index 249caf901..aaf3305a0 100644
--- a/natural/natural.d.ts
+++ b/natural/natural.d.ts
@@ -63,6 +63,9 @@ declare module "natural" {
   var PorterStemmerPt: {
     stem(token: string): string;
   }
+  var LancasterStemmer: {
+    stem(token: string): string;
+  }
 
   interface BayesClassifierCallback { (err: any, classifier: any): void }
   class BayesClassifier {