diff --git a/lib/libmbedtls/mbedtls/library/bignum.c b/lib/libmbedtls/mbedtls/library/bignum.c
index 5d4beca..8279d7d 100644
--- a/lib/libmbedtls/mbedtls/library/bignum.c
+++ b/lib/libmbedtls/mbedtls/library/bignum.c
@@ -777,8 +777,10 @@
     /* Ensure that target MPI has exactly the necessary number of limbs */
     if( X->n != limbs )
     {
+        short use_mempool = X->use_mempool;
+
         mbedtls_mpi_free( X );
-        mbedtls_mpi_init( X );
+        mpi_init( X, use_mempool );
         MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, limbs ) );
     }