diff --git a/library/bignum.c b/library/bignum.c
index f5130b4..0a95607 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1884,6 +1884,7 @@
     MPI_CHK( mpi_read_binary( X, buf, size ) );
 
 cleanup:
+    polarssl_zeroize( buf, sizeof( buf ) );
     return( ret );
 }