Simple Palindrome

[Inkanus]

Hi. I have simple program which checks if a string is a palindrome

def is_palindrome(i):
   if len(i) <= 1:
       return True
   else:
       if i[0] != i[len(i)-1]:
           return False
       else:
           return is_palindrome(i[1:len(i)-1])
print(is_palindrome("kajak"))

Unfortunately, when I write a word with a capital letter the result is "false". Please help. What to do and what to add to my code so that the same text in upper or lower case will be considered "True"?