diff --git a/polarssl/include/polarssl/bignum.h b/polarssl/include/polarssl/bignum.h
index e02db3f..26a1b36 100644
--- a/polarssl/include/polarssl/bignum.h
+++ b/polarssl/include/polarssl/bignum.h
@@ -83,7 +83,7 @@ typedef UINT64 uint64_t;
  * 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                              256      /**< Maximum number of bytes for usable MPIs. */
 #define POLARSSL_MPI_MAX_BITS                              ( 8 * POLARSSL_MPI_MAX_SIZE )    /**< Maximum number of bits for usable MPIs. */
 
 /*