dereferencing pointer to incomplete type

[std07181@xxxxxxxxx]

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Please help me with this problem.

My code:
#include <stdio.h>
#include <stdlib.h>
#include "katalogos.h"

#define PLITHOS 10
typedef struct diplistiva{
   int akorifi;
   int dkorifi;
   stixio pinakas[PLITHOS];
}diplistiva;

doublestack create()
{doublestack ThisStoiva;
        ThisStoiva=malloc(sizeof(diplistiva));
        ThisStoiva->akorifi = -1;  (HERE)
.
..
.
..
.
.

And my first part of types.h
typedef int stixio;

typedef struct  diplistiva *doublestack;

doublestack dimiourgia();


Why do i get that error?????

Please answer me as soon as possible it is very important