Cant assign missing values to string variable in SPSS using the GUI

I am strugling recoding missing values in SPSS using the graphical user interface. I can easily recode numeric variables using the GUI and the dialogue box shown below:

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But when i enter a string variable into the same dialogue box the option to define the new value as "System-missing" is not available:

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Surely such a simple problem can be solved without using the syntax editor?

Im using SPSS version 19


It is because system-missing values are defined only for numeric variables. You can define user-missing values for strings. For example, recode to some unused string value, like "99999" and set the value "99999" as user-missing afterwards.

IBM SPSS Statistics 19 Command Syntax Reference, page 55:

System-missing values cannot be generated for string variables, since any character is a legal string value.