Syntax error before a structure

This is a file name valid.c

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "valid.h"
#include "structure.h"

int checkCode(char* codeString,DATA_T* pResult)
{
    int status = 1;
    int i = 0;
    char countryCode[3];
    char passportNum[13];

    if((strlen(codeString)<11)||(strlen(codeString)>15))
        {
        status = ERR_BADFORM;
        }
    else if (codeString[2] != '-')
        {
        status = ERR_BADFORM;
        }
    else
        {
        /* check that the first two are alphabets */
        for (i = 0; (i < 2) && (status > 0); i++)
            {
            if (!isalpha(codeString[i]))
                {
                status = ERR_CODE;
                }
            if ((codeString[i]<=97)||(codeString[i]>=122))
                {
                codeString[i] = codeString[i] - 32;
                }
            }
        /* check that all other chars are digits */
        for (i = 2; (i < 13) && (status > 0); i++)
            {
            if (!isdigit(codeString[i]))
                {
                status = ERR_NUM;
                }
            }
            /* If the status is still positive, then we know the format is good */
            if (status > 0)
                {
                sscanf(codeString,"%s-%s",countryCode,passportNum);
                strcpy(pResult->passportID,countryCode);
                strcat(pResult->passportID,"-");
                strcat(pResult->passportID,passportNum);
                }
        }

    return status;
}

This is a file name valid.h

Code:

#define ERR_BADFORM     -10
#define ERR_CODE        -11
#define ERR_NUM         -12

int checkCode(char* codeString,DATA_T * pResult);

This is a file name structure.h

Code:

typedef struct
{
    char passportID[16];        /* Passport ID of the user */
    char firstName[30];         /* First name of the user */
    char lastName[30];          /* Last name of the user */
    char expireDate[10];        /* Expiration date of the passport */
    char entryDate[10];         /* Date of last entry into Thailand */
    char exitDate[10];          /* Date of last exit from Thailand */
    char visaType[30];          /* Type of visa */
} DATA_T;

I've been getting error in the valid.h saying that
the red line: error: syntax error before DATA_T
Can anyone help me with this?

Thank you

structure.h follows valid.h in your include list, so the compiler knows nothing about DATA_T in valid.h.

Thanks a lot ^^