Coding question? Following yields error, not sure how to fix?

Can someone tell me how to fix the following error? I am not a software guy and have tried multiple things but not figured it out.

H file:

Code:

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typedef struct mainScreen_t{
    uint8_t line;
    uint8_t position;
    char value[16];
}mainScreen_t;


const mainScreen_t Screen1 = {0, 10, {"GPS"}};
const mainScreen_t Screen2 = {1, 10, {"A/D"}};

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C file:

Code:

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mainScreen_t lvl_1[LCD_MAIN_MENUS] = {Screen1, Screen2};

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Error:

Code:

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"../main.c", line 41: error #28: expression must have a constant value

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I've no idea, it works for me.

Code:

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$ cat bar.c
#include <stdio.h>
#include <stdint.h>

typedef struct mainScreen_t{
    uint8_t line;
    uint8_t position;
    char value[16];
}mainScreen_t;

#define LCD_MAIN_MENUS 2
 
const mainScreen_t Screen1 = {0, 10, {"GPS"}};
const mainScreen_t Screen2 = {1, 10, {"A/D"}};

mainScreen_t lvl_1[LCD_MAIN_MENUS] = {Screen1, Screen2};

int main()
{
    printf("%s\n", lvl_1[0].value);
}
$ gcc bar.c
$ ./a.out
GPS
$ gcc -std=c89 -ansi -pedantic bar.c
$ ./a.out
GPS

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What compiler are you using?