diff --git a/library/bignum.c b/library/bignum.c
index 8864292..25fe8be 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1881,6 +1881,7 @@
     MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( X, buf, size ) );
 
 cleanup:
+    mbedtls_zeroize( buf, sizeof( buf ) );
     return( ret );
 }