Microsoft VBScript runtime error '800a005e'

I had a ASP Function that has been working fine to add left or right padding to a string. Something must have changed on the server as I now get a
Microsoft VBScript runtime error '800a005e'
Invalid use of Null

<%Function Lpad (MyValue, MyPadChar, MyPaddedLength)
Lpad = string(MyPaddedLength - Len(MyValue),MyPadChar) & MyValue
End Function
 
Function Rpad (MyValue, MyPadChar, MyPaddedLength)
Rpad = MyValue & string(MyPaddedLength - Len(MyValue), MyPadChar)
End Function %>

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