diff --git a/library/ecdh.c b/library/ecdh.c
index c572687..30c5f9f 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -637,6 +637,10 @@
         return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
 
     *olen = ctx->grp.pbits / 8 + ( ( ctx->grp.pbits % 8 ) != 0 );
+
+    if( ctx->grp.id == MBEDTLS_ECP_DP_CURVE25519 )
+        return mbedtls_mpi_write_binary_le( &ctx->z, buf, *olen );
+
     return mbedtls_mpi_write_binary( &ctx->z, buf, *olen );
 }