diff --git a/src/Maybe.ts b/src/Maybe.ts
index b711ff66..bad14b35 100644
--- a/src/Maybe.ts
+++ b/src/Maybe.ts
@@ -208,7 +208,8 @@ class Just<T> implements Maybe<T> {
   }
 
   toJSON(): T {
-    return this.__value
+    const value: any = this.__value
+    return value instanceof Date ? value.toJSON() : value
   }
 
   equals(other: Maybe<T>): boolean {