diff --git a/types/meteor/ejson.d.ts b/types/meteor/ejson.d.ts
index a6294fb8be..3ea090a7d2 100644
--- a/types/meteor/ejson.d.ts
+++ b/types/meteor/ejson.d.ts
@@ -1,6 +1,6 @@
 interface EJSONableCustomType {
-    clone(): EJSONableCustomType;
-    equals(other: Object): boolean;
+    clone?(): EJSONableCustomType;
+    equals?(other: Object): boolean;
     toJSONValue(): JSONable;
     typeName(): string;
 }