C: fscanf() on a hexadecimal giving me incorrect values

I've looked everywhere trying to figure out what I'm doing wrong and can't seem to figure out WHY this block of code isn't handling hexadecimal numbers correctly.

FILE *listFile = fopen(argv[1], "r");

unsigned int hexIndex;

if(listFile == NULL){
    printf("error\n");
    return 0;
}

while(!feof(listFile))
{
    fscanf(listFile, "%x\n", &hexIndex);

    printf("hexindex %d\n", hexIndex);
    if(hashInsert(hexIndex) == 0)
    {
        printf("uniques: %d\n", uniques);
        uniques++;
    }
}

For example, given a file with the following 3 hexadecimal addresses:

0xFFFFFFFFFF

0x7f1a91026b00

0x7f1a91026b03

The program prints out:

hexindex -1

hexindex -1862112512

hexindex -1862112509

which I'm 100% sure is incorrect. I've spent hours trying to figure out what I've done wrong, and I feel that I might be overlooking something simple. I've tried using different integer types like size_t, longs, etc. but run into the same exact output every time.

Can anybody give me some insight as to what I might be doing wrong?