diff --git a/sendgrid/helpers/mail/substitution.py b/sendgrid/helpers/mail/substitution.py
index d0e59837e..d515e885b 100644
--- a/sendgrid/helpers/mail/substitution.py
+++ b/sendgrid/helpers/mail/substitution.py
@@ -48,7 +48,7 @@ def value(self):
 
         :rtype value: string
         """
-        return self._value
+        return str(self._value) if isinstance(self._value, int) else self._value
 
     @value.setter
     def value(self, value):