diff --git a/15_optional_positional_params.dart b/15_optional_positional_params.dart
index 74d81b8..68ed67e 100644
--- a/15_optional_positional_params.dart
+++ b/15_optional_positional_params.dart
@@ -12,7 +12,7 @@ void main() {
 }
 
 // Required Parameters
-void printCities(String name1, String name2, String name3) {
+void printCities(var name1, var name2, var name3) {
 
 	print("Name 1 is $name1");
 	print("Name 2 is $name2");
@@ -20,9 +20,10 @@ void printCities(String name1, String name2, String name3) {
 }
 
 // Optional Positional Parameters
-void printCountries(String name1, [String name2, String name3]) {
+void printCountries(var name1, [var name2,  var name3]) {
 
 	print("Name 1 is $name1");
 	print("Name 2 is $name2");
 	print("Name 3 is $name3");
 }
+//String cannot be null since new rule