diff --git a/Conversions/RailwayTimeConversion.js b/Conversions/RailwayTimeConversion.js
index fd4f9a5dad..15f837b0da 100644
--- a/Conversions/RailwayTimeConversion.js
+++ b/Conversions/RailwayTimeConversion.js
@@ -18,7 +18,7 @@
 const RailwayTimeConversion = (timeString) => {
   // firstly, check that input is a string or not.
   if (typeof timeString !== 'string') {
-    return new TypeError('Argument is not a string.')
+    throw new TypeError('Argument is not a string.')
   }
   // split the string by ':' character.
   const [hour, minute, secondWithShift] = timeString.split(':')
diff --git a/Conversions/test/RailwayTimeConversion.test.js b/Conversions/test/RailwayTimeConversion.test.js
index 0e49af3b7f..6579420049 100644
--- a/Conversions/test/RailwayTimeConversion.test.js
+++ b/Conversions/test/RailwayTimeConversion.test.js
@@ -19,3 +19,7 @@ test('The RailwayTimeConversion of 11:20:00PM is 23:20:00', () => {
   const res = RailwayTimeConversion('11:20:00PM')
   expect(res).toEqual('23:20:00')
 })
+
+test('The RailwayTimeConversion throws when input is not a string', () => {
+  expect(() => RailwayTimeConversion(1120)).toThrowError()
+})