diff --git a/programs/pkey/rsa_sign.c b/programs/pkey/rsa_sign.c
index c9522c8..8e657a7 100644
--- a/programs/pkey/rsa_sign.c
+++ b/programs/pkey/rsa_sign.c
@@ -164,7 +164,7 @@
         goto exit;
     }
 
-    for( i = 0; i < rsa.len; i++ )
+    for( i = 0; i < rsa.MBEDTLS_PRIVATE(len); i++ )
         mbedtls_fprintf( f, "%02X%s", buf[i],
                  ( i + 1 ) % 16 == 0 ? "\r\n" : " " );