diff --git a/include/polarssl/bignum.h b/include/polarssl/bignum.h
index cd7592c..992ed8e 100644
--- a/include/polarssl/bignum.h
+++ b/include/polarssl/bignum.h
@@ -90,7 +90,7 @@
  * Note: Calculations can results temporarily in larger MPIs. So the number
  * of limbs required (POLARSSL_MPI_MAX_LIMBS) is higher.
  */
-#define POLARSSL_MPI_MAX_SIZE                              512      /**< Maximum number of bytes for usable MPIs. */
+#define POLARSSL_MPI_MAX_SIZE                              1024     /**< Maximum number of bytes for usable MPIs. */
 #endif /* !POLARSSL_MPI_MAX_SIZE */
 
 #define POLARSSL_MPI_MAX_BITS                              ( 8 * POLARSSL_MPI_MAX_SIZE )    /**< Maximum number of bits for usable MPIs. */